Image-formation material and infrared absorber

ABSTRACT

A heat mode-applicable image-formation material having high sensitivity and excellent image-forming property, and a novel infrared absorber which can be suitably used in this material. The present invention relates to a substrate carrying thereon an image-formation layer which contains an infrared absorption agent. The agent has at least one surface orientation group in the molecule, and solubility of the image-formation layer in an alkaline aqueous solution is changed by action of radiation in the near-infrared range. Preferable as the infrared absorbing agent is an infrared absorber comprising, in a molecule thereof, a fluorine-containing substituent which have at least 5 fluorine atoms, or a polymethine chain of at least 5 carbon atoms and an alkyl group of at least 8 carbon atoms, said alkyl group being connected to the polymethine chain via any of nitrogen, oxygen and sulfur.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 09/871,724,filed Jun. 4, 2001 now U.S. Pat. No. 6,727,037 which in turn claimspriority to Japanese Application No. 2000-169180, filed Jun. 6, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a positive or negative image-formationmaterial which can be recorded image-wise by exposure to an infraredlaser and in which solubility of a recording layer at exposed portionschanges, and to an infrared absorber which can be suitably used in theimage-formation material. More particularly, the present inventionrelates to an image-formation material with an infrared layer, which canbe recorded by exposure to an infrared laser or the like in thenear-infrared range, and particularly which is suitable for aplanographic printing plate used for so-called direct plate formationwhich can provide plate formation directly from digital signals ofcomputers and the like, and to an infrared absorber having a surfaceorientation group, which absorber is suitable for application in theimage-formation material.

2. Description of the Related Art

Recently, with the development of solid lasers and semiconductor lasershaving an emitting region in near-infrared to infrared ranges, systemsusing infrared lasers and providing direct plate formation from digitaldata of computers have drawn attention.

JP-A No. 7-285275 discloses a positive-type planographic printingmaterial for infrared lasers used in direct plate formation. Thisinvention is an image-recording material obtained by adding to analkaline aqueous solution-soluble resin a substance which absorbs lightand generates heat, and a positive photosensitive compound such as aquinonediazide compound or the like. The positive photosensitivecompound acts in image portions as a solution inhibitor thatsubstantially decreases solubility of the alkaline aqueoussolution-soluble resin, and is decomposed in non-image portions by heat,leading to a loss of solution-inhibiting ability. Resultantly, thepositive photosensitive compound can be removed by development, to forman image.

On the other hand, it is known that onium salts and alkali-insolublecompounds which can form hydrogen bonds act to suppressalkali-solubility of an alkali-soluble polymer. Regarding animage-formation material for infrared lasers, WO97/39894 describes thata composition using a cationic infrared absorber as an agent to suppressdissolution of an alkaline water-soluble polymer shows a positiveaction. This positive action is such that an infrared absorber absorbslaser light and an effect of suppressing dissolution of a polymer filmat irradiated portions is reduced by generated heat, to form an image.

Further, as a method for forming negative images, there is a recordingmethod in which a polymerization reaction is allowed to occur using, asan initiator, radicals generated by light or heat. The reaction cures arecording layer at exposed portions, forming image portions. Regardingsuch printing plates having a recording layer which is polymerized bylight or heat, there are known technologies using, as a photosensitivelayer, photopolymerizable or heat-polymerizable compositions asdescribed in JP-A Nos. 8-108621 and 9-34110.

Regarding image-forming properties of the above-mentioned variousrecording materials, there is a problem in that, although energysufficient for an image formation reaction is obtained at the surface ofa sensitive material irradiated by a laser, thermal diffusion to asubstrate is extensive, due to excellent thermal diffusion, andparticularly due to excellent heat conductivity when a generally-usedaluminum substrate is used as the substrate. Consequently, energy is notsufficiently utilized for forming images, leading to low sensitivity.With this problem, a sufficient effect of reducing suppression ofdissolution or an effect of promoting a reaction by polymerization maynot be obtained in deep portions of the sensitive material.Consequently, the occurrence of alkali development at exposedportions/non-exposed portions may not be fully realized, such thatexcellent images cannot be obtained, and furthermore, developinglatitude, that is, tolerable range which can afford good image-formationwhen concentration of an alkaline developing solution is varied, isnarrow.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is-to provide animage-formation material having high sensitivity and excellentimage-forming property, and a novel infrared absorber which can besuitably used in this material.

The present inventor has intensively studied for the purpose ofimproving sensitivity and image-forming property of image-formationmaterials, and has consequently found that both sensitivity andimage-forming property can be improved by using an infrared absorptionagent having a specific substituent. Further, the inventor has found anovel infrared absorber that can be suitably used in this agent,leading-to completion of the present invention.

That is, the image-formation material of the present invention is a heatmode-applicable image-formation material, the image-formation materialhaving: a substrate; and an image-formation layer on the substrate whichcontains an infrared absorption agent having at least one surfaceorientation group in a molecule thereof, solubility of theimage-formation layer in an alkaline aqueous solution being changeableby action of near-infrared range radiation.

Here, in a preferable embodiment, the above-mentioned infraredabsorption agent is an infrared absorber having at least one surfaceorientation group selected from fluorine-containing substituents andlong chain alkyl groups.

Further, the infrared absorber of the present invention is characterizedin that it has in the molecule a fluorine-containing substituent havingat least 5 fluorine atoms.

As the infrared absorber having such a fluorine substituent, there arespecifically exemplified infrared absorbers which manifest absorption inthe near-infrared range, represented by the following general formulae(1) to (3).

In general formula (1): each of R_(F) ¹ and R_(F) ² independentlyrepresents a fluorine-containing substituent having at least 5 fluorineatoms; each of X¹ and X² independently represents —CR⁹R¹⁰—, —S—, —S—,—NR¹¹—, —CH═CH— or —O—. R¹ to R⁸ each independently represents ahydrogen atom, alkyl group, alkoxy group or halogen atom. R¹ to R⁸ mayrepresent a plurality of atoms such that at least one of pairs R¹ andR³, R² and R⁴, R⁵ and R⁷, R⁶ and R⁸, R¹ and X¹, or R² and X² can bemutually connectable to form an aliphatic 5-membered ring or 6-memberedring, an aromatic 6-membered ring or a substituted aromatic 6-memberedring.

R⁹ and R¹⁰ each independently represents an alkyl group, or represent═CH— which are combined to form a ring; R¹¹ represents an alkyl group.

Z¹ represents a heptamethine group, which may have one or moresubstituents selected from alkyl groups, halogen atoms, amino groups,arylthio groups, alkylthio groups, aryloxy groups, alkoxy groups,barbituric groups and thiobarbituric groups, and which may include acyclohexene or cyclopentene ring formed by mutually bonding substituentson two methine carbons of the heptamethine group, which ring may furtherhave a substituent selected from alkyl groups and halogen atoms.

X⁻ represents a counter ion necessary for neutralizing an electriccharge.

In general formula (2): R_(F) ³ represents a fluorine-containingsubstituent having at least 5 fluorine atoms. X³ represents —NH—, —O— or—S—. Z² represents a polymethine chain of at least 5 carbon atoms. Eachof R¹² and R¹³ independently represents an alkyl group. These alkylgroups may have a substituent, and as preferable substituents, arylgroups such as a phenyl group, toluyl group and the like, alkoxy groupssuch as a methoxy group, ethoxy group, methoxyethoxy group and the like,aryloxy groups such as a phenoxy group, toluyloxy groups and the like,acid groups such as a carboxyl group, sulfonic group and the like orsalts thereof, quaternary ammonium groups such as a triethylammoniumgroup, tributylammonium group and the like, a hydroxyl group, amidegroups and the like are exemplified.

X¹, X², R¹ to R⁸ and X⁻ are as defined for the above-mentioned generalformula (1).

In general formula (3): each of R_(F) ⁴, R_(F) ⁵, R_(F) ⁶ and R_(F) ⁷independently represents a fluorine-containing substituent having atleast 5 fluorine atoms or an alkyl group, and at least one of R_(F) ⁴,R_(F) ⁵, R_(F) ⁶ and R_(F) ⁷ represents a fluorine-containingsubstituent having at least 5 fluorine atoms. Z³ represents apentamethine group, which may have a substituent selected from halogenatoms, hydroxyl groups, alkyl groups, aryl groups and heterocyclicgroups. Here, the alkyl group and aryl group may further have asubstituent, and as preferable further substituents, aryl groups such asa phenyl group, toluyl group and the like, alkoxy groups such as amethoxy group, ethoxy group, methoxyethoxy group and the like, aryloxygroups such as a phenoxy group, toluyloxy groups and the like, areexemplified. Further, this pentamethine group may also contain acyclohexene or cyclopentene ring formed by mutually bonding substituentson two methine carbons of the pentamethine group, which ring may furtherhave a substituent selected from alkyl groups and halogen atoms.

X⁻ represents a counter ion necessary for neutralizing an electriccharge.

Further, the infrared absorber of the present invention may preferablyhave a polymethine chain of at least 5 carbon atoms, and an alkyl groupof at least 8 carbon atoms, the alkyl group being connected to thepolymethine chain via any of nitrogen, oxygen and sulfur.

As such an infrared absorber, infrared absorbers of the followinggeneral formula (4) are specifically listed.

In general formula (4): R¹⁴ represents an alkyl group of at least 8carbon atoms. X³ represents —NH—, —O— or —S—. Z² represents apolymethine chain of at least 5 carbon atoms. Each of R¹² and R¹³independently represents an alkyl group, and may have the samesubstituents as in the general formula (2).

X¹, X², R¹ to R⁸ and X⁻ are as defined for the above-mentioned generalformula (1).

Although action of the present invention is not clear, it is believedthat by using an infrared absorber which manifests absorption in thenear-infrared range and has a surface orientation group as the infraredabsorption agent to be used in the image-formation material of thepresent invention, an infrared absorption agent is localized on theoutermost surface (air interface) of a photosensitive layer. Thus,diffusion of heat generated near the surface into a substrate issuppressed, and the generated heat is utilized efficiently for formingimages. Consequently, an increase in sensitivity can be attained.

Further, from the investigations of the present inventor, it is apparentthat when a resin layer containing an infrared absorber having a surfaceorientation group is irradiated by an infrared laser, the surfacecontact angle of the resin layer increases. Resultantly, in theimage-formation material of the present invention, permeability of adeveloping solution at exposed portions of the image-formation layerlowers. Therefore, particularly in the case of use as a negativerecording material, there is also a benefit in that discrimination canbe expanded.

In the present invention, “heat mode-applicable” means that recording byheat mode exposure is possible. The definition of the heat mode exposurein the present invention will be explained in detail. As described inHans-Joachim Timpe, IS&Ts NIP 15: 1999 International Conference onDigital Printing Technologies, P. 209, it is known that there are twomodes with respect to a process in which photo-excitation of alight-absorbing substance (for example, dye) in a photosensitivematerial causes a chemical or physical change to form an image. One is aso-called photon mode in which a light-absorbing substance which hasbeen photo-excited is deactivated by a certain photochemical interaction(for example, energy transfer or electron transfer) with anotherreactive substance in the photosensitive material, and the resultingactivated reactive substance causes a chemical or physical changerequired for the above mentioned image-formation. The other is aso-called heat mode in which a light-absorbing substance that has beenphoto-excited is deactivated via heat emission, and a reactivesubstance, by utilizing this heat, causes a chemical or physical changerequired for the image-formation. Additionally, special modes such asablation, in which substances are explosively spattered by locallyconcentrated light energy, multi-photon absorption, in which onemolecule absorbs a lot of photons at one time, and the like are listed.However, these modes are omitted in this specification.

An exposure process utilizing one of the above-mentioned modes is calledphoton mode exposure or heat mode exposure. A technical differencebetween the photon mode exposure and the heat mode exposure is whetheror not the energy amount of several photons of exposure light can beadded and utilized for the energy amount required for the intendedreaction. For example, it is hypothesized to use n photons to cause acertain reaction. In photon mode exposure, it is impossible to add theenergy amount of photons to each other, due to quantum laws ofconservation of energy and momentum, since a photochemical interactionis utilized. That is, to cause some reaction, the relationship: “energyamount of one photon≧energy amount of reaction” must apply. On the otherhand, in the heat mode exposure, it is possible to add and utilize theenergy amount of multiple photons, since heat is generated fromphoto-excitation; thus, the light energy is converted into heat andutilized. Therefore, the relationship: “energy amount of nphotons≧energy amount of reaction” is sufficient. However, this additionof energy amounts is limited by thermal diffusion. That is, if the nextlight-excitation-de-activation process occurs and heat is generateduntil heat is liberated by thermal diffusion from the exposed portion(reaction point) in question, the heat is invariably accumulated andadded, leading to an increase in temperature of this part. However, ifthe next generation of heat is delayed, the heat is liberated and notaccumulated. That is, in the heat mode exposure, there is a differenceof result between a case of irradiation with light having a high energyamount for a short period of time and a case of irradiation with lighthaving a low energy amount for a long period of time, even when thetotal exposure energy amount is the same. The case of a short period oftime is advantageous for accumulation of heat.

Of course, in the photon mode exposure, such a phenomenon basically doesnot occur, although analogous phenomenon may occur in some cases by theinfluence of diffusion of subsequent reaction species.

That is, from the standpoint of properties of a photosensitive material,inherent sensitivity of a photosensitive material (energy amount forreaction required to form image) is constant with respect to exposurepower density (W/cm²)(=energy density per unit time) in the photon mode,while in the heat mode, the inherent sensitivity of the photosensitivematerial increases with the exposure power density. Therefore, whenmodes are compared, if an exposure time appropriate to maintainpractically necessary productivity of an image-recording material isactually fixed, in the photon mode exposure, a high sensitivity of about0.1 mJ/cm² can be usually attained. However, since a reaction occurs atany lower exposure amount, a problem of low-exposure fogging atnon-exposed portions tends to occur. On the other hand, in the heat modeexposure, reaction occurs only at an exposure amount of a certain levelor more, and an exposure amount of about 50 mJ/cm² is usually necessaryin view of a relationship with thermal stability of a photosensitivematerial. However, problems with low exposure light are avoided.

Thus, in the heat mode exposure in actuality, an exposure power densityon the surface of a photosensitive material of 5,000 W/cm² or more,preferably 10,000 W/cm² or more is necessary. Use of a laser with a highpower density of 5.0×10⁵ W/cm² or more is not preferable, due toproblems such as occurrence of abrasion, staining of a light source, andthe like, though this is not described in detail herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Infrared Absorption Agent Having in a Molecule at Least One SurfaceOrientation Group]

The infrared absorption agent used in the image-formation material ofthe present invention is an infrared absorption agent having in themolecule thereof at least one surface orientation group. By action ofthis surface orientation group, when a coating solution of animage-formation layer is applied and dried to form the image-formationlayer, the infrared absorption agent shifts to places near the surfaceof the image-formation layer, and is localized.

As such a surface orientation group, there are listed functional groupshaving high hydrophobicity, such as those used as a hydrophobic group ofa surfactant. Among these, fluorine-containing substituents, long chainalkyl groups having 8 or more carbon atoms, polysiloxane groups(silicone groups) and the like are suitably listed. These surfaceorientation groups may be present alone in a molecule, or a plurality ofsuch groups may be present in a molecule.

Regarding function of an infrared absorption agent contained in theimage-formation material of the present invention, the agent generatesheat when irradiated with radiation in the near-infrared range,typically by exposure to infrared light, and recording is conducted bythis heat, similarly to a usual infrared absorption agent contained in arecording material which can effect image-formation by exposure in theinfrared range. Therefore, it is required that infrared laser light isefficiently converted into heat by the infrared absorption agentlocalized on the surface of the image-formation layer, and isefficiently used in a reaction for forming images.

The infrared absorption agent herein used manifests absorption in thenear-infrared range, and specifically, manifests absorption in awavelength range from 720 nm to 1200 nm, and preferably has anabsorption maximum in the wavelength range from 720 nm to 1200 nm.

The present inventor has investigated infrared absorbers having asurface orientation group selected from fluorine-containingsubstituents, long chain alkyl groups and the like, and have found anovel infrared absorber which can be suitably used in theimage-formation material of the present invention. This infraredabsorber is an infrared absorber having a fluorine-containingsubstituent having at least 5 fluorine atoms, which is a surfaceorientation group, or a near-infrared absorber having a polymethinechain that has 5 or more carbon atoms and having an alkyl group that has8 or more carbon atoms connected to the polymethine chain via any ofnitrogen, oxygen and sulfur.

These novel infrared absorbers are described below.

As the infrared absorber having a fluorine-containing substituent havingat least 5 fluorine atoms, infrared absorbers having in the molecule achromophore which manifests absorption in the near-infrared range as abase skeleton and having at least one of the above-mentionedsubstituents in the molecule are listed.

As the fluorine-containing substituent having at least 5 fluorine atoms,there are listed, for example, —(CH₂)_(n)(CF₂)_(m)CF₃,—(CH₂)_(n)CF₂(CF₂)_(m)H (wherein, n represents an integer from 0 to 6and m represents an integer from 2 to 16), groups having fluorine atomsat five positions excepting the connecting group of a benzene ring, apentafluorophenyl group and the like.

Of these, infrared absorbers having a polymethine chain of theabove-mentioned general formulae (1) to (3) are listed as preferableexamples, in view of light-heat converting function and stability as aninfrared absorber.

The infrared absorbers as described above are specifically described indetail, but do not limit the scope of the present invention.

The structures of the following exemplified compounds (IR-1) to (IR-24)are shown specifying a counter ion X⁻, since base skeletons,fluorine-containing substituents, other substituents present onchromophores and chromophores have electric charge.

As compounds represented by the general formula (1), the followingexemplified compounds (IR-1) to (IR-15) are listed.

R¹ Z¹ X⁻ IR-1 —CH₂(CF₂)₆CF₃ Cl

IR-2 —CH₂(CF₂)₆CF₃

ClO₄ ⁻ IR-3 —CH₂(CF₂)₆CF₃

ClO₄ ⁻ IR-4 —CH₂CH₂(CF₂)₅CF₃ Cl

IR-5 —CH₂CH₂(CF₂)₅CF₃ Cl ClO₄ ⁻ IR-6

(CF₂)₂CF₃ Cl

IR-7 —CH₂(CF₂)₂CF₃ Cl ClO₄ ⁻ IR-8 —CH₂CH₂(CF₂)₅CF₃

None

R² Z² X⁻ IR-9 —CH₂(CF₂)₆CF₃ Cl

IR-10 —CH₂CH₂(CF₂)₅CF₃ Cl ClO₄ ⁻ IR-11 —CH₂(CF₂)₂CF₃ Cl ClO₄ ⁻

R₃ Z³ X⁻ IR-12 —CH₂(CF₂)₆CF₃ Cl

IR-13 —CH₂CH₂(CF₂)₅CF₃ —NPh₂ ClO₄ ⁻

R⁴ X⁻ IR-14 —CH₂(CF₂)₆CF₃ ClO₄ ⁻ IR-15 —CH₂CH₂(CF₂)₅CF₃ ClO₄ ⁻

As compounds represented by the general formula (2), the followingexemplified compounds (IR-16) to (IR-19) are listed.

R¹ Z¹ X⁻ IR-16 —CH₃ —SCH₂CH₂(CF₂)₅CF₃ ClO₄ ⁻ IR-17 —CH₃ —NH CH₂(CF₂)₆CF₃ClO₄ ⁻

R² Z² X⁻ IR-18 —CH₃ —SCH₂CH₂(CF₂)₅CF₃

IR-19 —CH₃ —SCH₂CH₂(CF₂)₅CF₃ ClO₄ ⁻

As compounds represented by the general formula (3), the followingexemplified compounds (IR-20) to (IR-24) are listed.

R⁵ R⁶ X⁻ IR-20 —CH₂CH₂OCO(CF₂)₆CF₃ —CH₂CH₃ BF⁴⁻ IR-21—CH₂CH₂OCO(CF₂)₆CF₃ —CH₂CH₂OCO(CF₂)₆CF₃ ClO₄ ⁻

R⁷ R⁸ n X⁻ IR-22 —CH₂CH₂OCO(CF₂)₆CF₃ —CH₂CH₃ 2 BF⁴⁻ IR-23—CH₂CH₂OCO(CF₂)₆CF₃ —CH₂CH₂OCO(CF₂)₆CF₃ 2 ClO₄ ⁻ IR-24—CH₂CH₂OCO(CF₂)₆CF₃ —CH₂CH₃ 3 ClO₄ ⁻

Next, the near-infrared absorber having a polymethine chain that has 5or more carbon atoms and having an alkyl group that has 8 or more carbonatoms connected to the polymethine chain via any of nitrogen, oxygen andsulfur will be described.

As the polymethine chain, a heptamethine chain, pentamethine chain,nonamethine chain and the like are preferable from the standpoints ofstability and absorption wavelength, and a heptamethine chain andpentamethine chain are particularly preferable.

Of these, infrared absorbers of the above-mentioned general formula (4)are listed as preferable examples in view of light-heat convertingfunction and stability as an infrared absorber, but the scope of theinvention is not restricted to these.

The structures of the following exemplified compounds (IR-25) to (IR-36)are shown by specifying a counter ion X⁻, since base skeletons,fluorine-containing substituents, other substituents present onchromophores, and chromophores have electric charge.

R⁹ Z⁴ X⁻ IR-25 —CH₃ —S(CH₂)₁₇CH₃ ClO₄ ⁻ IR-26 —CH₃ —S(CH₂)₁₅CH₃ BF₄ ⁻IR-27 —CH₂CH₂CH₃ —O(CH₂)₁₉CH₃ ClO₄ ⁻ IR-28 —CH₃ —NH(CH₂)₁₇CH₃ ClO₄ ⁻

Z⁵ X⁻ IR-29 —S(CH₂)₁₇CH₃

IR-30 —O(CH₂)₁₉CH₃ ClO₄ ⁻ IR-31 —NH(CH₂)₁₇CH₃ ClO₄ ⁻

R¹¹ Z⁶ X⁻ IR-32 —CH₃ —S(CH)₁₇CH₃

IR-33 —CH₃ —S(CH)₁₇CH₃ ClO₄ ⁻ IR-34 —CH₂CH₂CH₃ —NH(CH₂)₁₇CH₃ ClO₄ ⁻

R¹² Z⁷ X⁻ IR-35 —CH₃ —S(CH)₁₇CH₃

IR-36 —CH₃ —S(CH)₁₇CH₃ ClO₄ ⁻

As the infrared absorption agent which can be suitably used in theimage-formation material of the present invention, the followingexemplified compounds (IR-37) to (IR-42) having an alkyl group having 8or more carbon atoms outside the polymethine chain are also listed.

Next, a method of producing the infrared absorption agent as describedabove will be described.

Infrared absorption agents of the above-mentioned general formulae (1)to (4) can be produced by a known organic synthesis technology.Specifically, they can be synthesized by synthetic methods described inU.S. Pat. No. 5,441,866, Zh. Org. Khim. vol. 28 (No. 10) pp. 2156 to2164 (1992), EP No. 465,543 A1, J. Org. Chem. (Journal of OrganicChemistry) vol. 57 (No. 17) pp. 4578 to 4580 (1992), Japanese PatentRegistration No. 2758136, Justus Liebigs Ann. Chem, vol. 623, pp. 204 to216 (1959), Ukr. Khim. Zh. vol. 22, pp. 347 to 348 (1956), Chem.Heterocycl. Comp. vol. 18, pp. 334 to 336 (1982), J. Heterocycl. Chem.vol. 25, pp. 1321 to 1325 (1988), Japanese Patent Application Laid-Open(JP-A) No. 60-231766, and the like.

The infrared absorption agent may be added to an image-formationmaterial, and may then be added together with other components into animage-formation layer. Alternatively, when a layer other than arecording layer is provided, in producing a planographic printing plate,the infrared absorption agent may be added into this layer. Theseinfrared absorption agents may be added alone or in a mixture of two ormore.

In the present invention, these infrared absorption agents can be addedin a ratio of from 0.01 to 50 wt %, preferably from 0.1 to 20 wt %, andmore preferably from 0.5 to 15 wt %, based on the total weight of solidcomponents that form the image-formation layer of the image-formationmaterial. If the addition amount is less than 0.01 wt %, theimage-forming property thereof will deteriorate, and if added in anamount of over 50 wt %, there is a risk of occurrence of staining atnon-image portions in the case of use for a recording layer of aplanographic printing plate.

To the image-formation material of the present invention, in addition tothis infrared absorption agent, other pigments or dyes having infraredabsorbing property can be added for the purpose of the improvingimage-forming property.

As a pigment, commercially available pigments, and pigments described inColor Index (C.I.) manual, “Saishin Ganryo Binran” (“Current PigmentManual”, edited by Nippon Ganryo Gijutsu Kyokai, 1977), “Saishin GanryoOyo Gijutsu” (“Current Pigment Application Technology”, published byCMC, 1986), “Insatsu Inki Gijutsu” (“Printing Ink Technology”, publishedby CMC, 1984) can be utilized.

As the pigments, black pigments, yellow pigments, orange pigments, brownpigments, red pigments, violet pigments, blue pigments, green pigments,fluorescent pigments, metal powder pigments, and additionally, polymerbond pigments, are listed. Specifically, insoluble azo pigments, azolakepigments, condensed azo pigments, chelate azo pigments,phthalocyanine-based pigments, anthraquinone-based pigments, peryleneand perynone-based pigments, thioindigo-based pigments,quinacridone-based pigments, dioxazine-based pigments,isoindolinone-based pigments, quinophthalone-based pigments, dyeing lakepigments, azine pigments, nitroso pigments, nitro pigments, naturalpigments, fluorescent pigments, inorganic pigments, carbon black and thelike can be used.

These pigments may be used without surface treatment, or may besurface-treated before use. As a method of surface treatment, a methodof surface coating with a resin or wax, a method of adhering asurfactant, a method of bonding a reactive substance (for example, asilane coupling agent, epoxy compound, polyisocyanate or the like) tothe surface of the pigment, and the like are envisaged. Theabove-mentioned surface treatment methods are described in “KinzokuSekken no Seishitsu to Oyo” (“Nature and Applications of Metal Soaps”,Sachi Publication), “Insatsu Inki Gijutsu” (“Printing Ink Technology”,published by CMC, 1984), and “Saishin Ganryo Oyo Gijutsu” (“CurrentPigment Application Technology”, published by CMC, 1986).

The particle size of the pigment is preferably from 0.01 μm to 10 μm,further preferably from 0.05 μm to 1 μm, and particularly preferablyfrom 0.1 μm to 1 μm. A particle size of the pigment of less than 0.01 μmis not preferable from the standpoint of instability of a dispersedsubstance in a coating solution for an image photosensing layer, and aparticle size of over 10 μm is not preferable from the standpoint ofuniformity of the image photosensing layer.

As a method of dispersing a pigment, known dispersing technologies usedin production of ink, production of toners, and the like can be used. Asa dispersing machine, an ultrasonic disperser, sand mill, attritor,pearl mill, super mill, ball mill, impeller, disperser, KD mill, colloidmill, Dynatron, triple screw roll mill, press kneader and the like arelisted. Details are described in “Saishin Ganryo Oyo Gijutsu” (“CurrentPigment Application Technology”, published by CMC, 1986).

As a dye, commercially available dyes and, known materials described inthe literature such as, for example, “Dye Manual” (edited by Yuki GoseiKagaku Kyokai, 1960) and the like can be used. Specifically, dyes suchas azo dyes, metal complex salt azo dyes, pyrazoloneazo dyes,anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneiminedyes, methine dyes, cyanine dyes, diimmonium dyes, aminium dyes and thelike are listed.

In the present invention, among these pigments and dyes, those whichabsorb infrared light or near-infrared light are particularly preferablesince they are suitable for use with lasers that emit infrared light ornear-infrared light.

As pigments that absorb infrared light or near-infrared light, carbonblack is suitably used. As a dye that absorbs infrared light ornear-infrared light, for example, cyanine dyes described in JP-A Nos.58-125246, 59-84356, 59-202829, 60-78787 and the like, methine dyesdescribed in JP-A Nos. 58-173696, 58-181690 and 58-194595 and the like,naphthoquinone dyes described in JP-A Nos. 58-112793, 58-224793,59-48187, 59-73996, 60-52940, 60-63744 and the like, squarylium dyesdescribed in JP-A No. 58-112792 and the like, cyanine dyes described inBritish Patent No. 434,875, and dihydroperimidine squarylium dyesdescribed in U.S. Pat. No. 5,380,635, etc. are listed.

Further, as the dye, near-infrared absorbing sensitizers described inU.S. Pat. No. 5,156,938 can also be used suitably, and particularlypreferably used are arylbenzo(thio)pyrylium salts described in U.S. Pat.No. 3,881,924, trimethinethiapyrylium salts described in JP-A No.57-142645 (U.S. Pat. No. 4,327,169), pyrylium-based compounds describedin JP-A Nos. 58-181051, 58-220143, 59-41363, 59-84248, 59-84249,59-146063 and 59-146061, cyanine dyes described in JP-A No. 59-216146,pentamethinethiopyrylium salts and the like described in U.S. Pat. No.4,283,475, pyrylium compounds described in JP-B Nos. 5-13514 and5-19702, Epolight III-178, Epolight III-130, Epolight III-125, EpolightIV-62A, and the like.

Further, as other examples particularly preferable as dyes,near-infrared absorption dyes of formulae (I) and (II) described in U.S.Pat. No. 4,756,993 are listed.

Since these pigments or dyes are used together with the above-mentionedspecific infrared absorption agent, the addition amount when added ispreferably from about 0.01 to 20 wt % based on the total amount of solidcomponents constituting the image-formation layer. In the case of a dye,the addition amount is particularly preferably from 0.5 to 10 wt %, andin the case of a pigment, the addition amount is particularly preferablyfrom 0.1 to 5 wt %. If the addition amount of the pigment or dye is lessthan 0.01 wt %, the effect of addition is not observable, and if over 20wt %, there is a risk of an undesirable influence on the effect ofincreased sensitivity that is to be provided by the above-mentionedspecific infrared absorption agent.

As other components of the image-formation material of the presentinvention, various known image-formation materials which can be recordedby radiation in the infrared range can be appropriately selected foruse.

First, a recording layer of which solubility in an alkaline aqueoussolution is changed by exposure with infrared light will be described.Such recording layers are classified into negative-type layers, in whichalkali-developing property is decreased by exposure to infrared light,and positive-type layers, in which developing property increasesinstead.

As a negative-type recording layer, known negative-type polar-conversionmaterial-based (changing between hydrophilicity and hydrophobicity),radical polymerization-based and acid catalyst crosslinking-based(including cation polymerization) recording layers are listed. Amongthese, radical polymerization-based and acid catalyst crosslinking-basedlayers are particularly preferable from the standpoint of printingendurance. In these layers, a radical or acid generated by irradiationor heating acts as an initiator or catalyst, and compounds constitutingthe recording layer cause a polymerization reaction or crosslinkingreaction, and cure, forming image portions.

As a positive-type recording layer, known positive-type polar-conversionmaterial-based (changing between hydrophobicity and hydrophilicity),acid catalyst decomposition-based and interaction release-based(heat-sensitive positive) recording layers are listed. Among these,particularly, positive-type polar conversion material-based layersobtained by thermal decomposition of sulfonate esters, and acid catalystdecomposition-based and interaction release-based layers are preferablefrom the standpoint of image quality. In these layers, by acid or heatenergy generated by irradiation or heating, a bond of a polymer compoundforming a layer is released or the like, leading to water-solubility oralkaline water-solubility, and such portions can be removed bydevelopment to form non-image portions. In any image-formation layer, apolymer compound which is insoluble in water and soluble in an alkalineaqueous solution is preferably contained as a layer constituentcomponent, that is, as a binder.

Next, image-formation layers are classified by image formation mechanismand described in detail.

<Radical Polymerization Layer>

The radical polymerization layer which can be used in theimage-formation material of the present invention contains a compoundthat generates a radical due to light or heat (hereinafter, referred toas a radical generator) and a compound which can be radical-polymerized(referred to as a polymerizable compound). For example, a radical isgenerated from a radical generator in an exposed portion by irradiationwith an infrared laser or the like, and this radical acts as aninitiator. Consequently, the polymerizable compound is cured by aradical polymerization reaction, to form an image portion. Thecombination of a radical generator and polymerizable compound to be usedherein can be appropriately selected for use, providing the strength ofa film formed by radical polymerization satisfies the requirements of arecording layer. Further, for improvement of reactivity of the radicalgenerator, promoters such as onium salts, reducing agents and the likecan also be used together therewith. As components which can be used ina radical polymerization layer, for example, compounds described asconstituent components of a heat polymerizable recording layer in JP-ANo. 8-108621, compounds described as constituent components of arecording layer in JP-A No. 9-34110, and the like can also be preferablyused.

(Radical Generator)

As the radical generator used in the radical polymerization layer, knownradical polymerization initiators used in a polymer synthesis reactionfor radical polymerization can be usually used without specificrestriction. There are exemplified azobisnitrile-based compounds such as2,2′-azobisisobutyronitrile, 2,2′-azobispropionitrile and the like;organic peroxides such as benzoyl peroxide, lauroyl peroxide, acetylperoxide, t-butyl perbenzoate, α-cumyl hydroperoxide, di-t-butylperoxide, diisopropyl peroxy dicarbonate, t-butyl peroxy isopropylcarbonate, peracids, alkyl peroxy carbamates, nitrosoarylacylamines andthe like; inorganic peroxides such as potassium persulfate, ammoniumpersulfate, potassium perchlorate and the like; azo or diazo-basedcompounds such as diazoaminobenzene, p-nitrobenzenediazonium,azobis-substituted alkanes, diazothioethers, arylazosulfones and thelike; tetraalkylthiuram disulfides such as nitrosophenylurea,tetramethylthiuram disulfide and the like; diaryl disulfides such asdibenzoyl disulfide and the like; dialkylxanthogenic disulfides,arylsulfines, arylalkylsulfones, 1-alkanesulfines and the like.

When the image-formation material of the present invention is recordedon with an infrared laser, sufficient sensitivity can be obtained evenwith a radical generator having a large activation energy, since thetemperature of the exposed surface may reach as high as 600° C. or more,depending on laser energy.

The activation energy for generating the radical from the radicalgenerator is preferably 30 kcal/mol or more, and as compoundsmanifesting such energy, azobisnitrile-based compounds and organicperoxides are listed. Among these, preferable are compounds havingexcellent stability at ambient temperature, manifesting high decomposingspeed in overheating, and becoming colorless in decomposing, and benzoylperoxide, 2,2′-azobisisobutyronitrile and the like are listed.

The above-mentioned radical generators may be used alone or in acombination of two or more, and are used in an amount of from about 0.5to 30 wt %, preferably from 2 to 10 wt % based on the total weight ofsolid components in a radical polymerization layer.

Further, compounds that generate a radical by interaction with an oniumsalt described later can also be suitably used. Specifically, halogencompounds (α-haloacetophenones, trichloromethyltriazines and the like),azo compounds, aromatic carbonyl compounds (benzoin esters, ketals,acetophonones, o-acyloxyiminoketones, acylphosphine oxides and thelike), hexaarylbisimidazole compounds, peroxides and the like arelisted, and preferably listed are bisimidazole derivatives disclosed as(A-1) to (A-4) in the above-mentioned JP-A No. 9-34110, page 16.

The latter radical generator attains high sensitivity by interactionwith an onium salt. As the onium salt which can be used together withthis radical generator, phosphonium salts, sulfonium salts, iodoniumsalts and ammonium salts described in the same publication, paragraphNos. [0022] to [0049] are listed.

The amount of the above-mentioned onium salt added is preferably from0.05 to 50% by weight based on the total weight of solid components inthe recording layer, although this may vary depending on the kind andused form of the onium salt.

Further, onium salts such as iodonium salts, sulfonium salts, phophoniumsalts, diazonium salts and the like which can be suitably used as anacid generator in <Acid crosslinking agents> described later can be usedalone as a radical generator without combination with theabove-mentioned radical generator, and an addition amount thereof ispreferably from 0.05 to 50% by weight based on the total weight of solidcomponents in a recording layer, although this may vary depending on thekind and used form.

(Polymerizable Compound)

As the polymerizable polymer compound which is polymerized to be curedby the radical generated by the radical generator, known monomers havinga polymerizable group can be used without specific restriction. As suchmonomers, there are specifically exemplified: mono-functional acrylatessuch as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropylacrylate and the like and derivatives thereof, or compounds obtained bysubstituting acrylate in these compounds with methacrylate, itaconate,crotonate, maleate and the like; bifunctional acrylates such aspolyethylene glycol diacrylate, pentaerythritol diacrylate, bisphenol Adiacrylate, diacrylate of ε-caprolactone adduct of hydroxypivalic acidneopentyl glycol, and the like, and derivatives thereof, or compoundslikewise obtained by substituting acrylate in these compounds withmethacrylate, and the like; polyfunctional acrylates such astrimethylolpropane tri(meth)acrylate, dipentaerythritol pentaacrylate,dipentaerythritol hexaacrylate, pyrogallol triacrylate and the like andderivatives thereof, or compounds obtained by substituting acrylate inthese compounds with methacrylate, and the like. Further, so-calledprepolymers which are obtained by introducing an acrylic acid ormethacrylic acid into an oligomer having suitable molecular weight andare endowed with a light polymerization property can also be suitablyused.

In addition to these, compounds described in JP-A Nos. 58-212994,61-6649, 62-46688, 62-48589, 62-173295, 62-187092, 63-67189, 1-244891and the like, and other compounds are listed. Further, compoundsdescribed in “11290 Chemical Products”, Kagaku Kogyo Nippo Sha, pp. 286to 294, compounds descried in “UV EB curing Hand Book” (raw materialschapter) Kobunshi Kanko Kai, pp. 11 to 65, and other compounds can alsobe suitably used.

Among these, compounds having two or more acrylic groups or methacrylicgroups in the molecule are preferable in the present invention. Further,those having a molecular weight of 10,000 or less, more preferably 5,000or less, are desirable. In the present invention, the polymerizablecompounds are selected from monomers and prepolymers having apolymerizable group, including also the above exemplified compounds, andcan be used alone, or in a combination of two or more provided there isno problem in compatibility and affinity, according to objectives.

A compound having an ethylenically-unsaturated group is contained in anamount preferably from 20 to 80 wt %, more preferably from 30 to 60 wt %in terms of solid components in the radical polymerization layer.

(Binder Resin)

In the recording layer, a binder resin is used, if necessary. As thebinder resin, polyester-based resins, polyvinylacetal-based resins,polyurethane-based resins, polyamide-based resins, cellulose-basedresins, olefin-based resins, vinyl chloride-based resins, (meth)acrylicacid-based resins, styrene-based resins, polycarbonate, polyvinylalcohol, polyvinylpyrrolidone, polysulfone, polycaprolactone resins,polyacrylonitrile resin, urea resins, epoxy resins, phenoxy resins,rubber-based resins and the like are listed. Further, resins having anunsaturated bond in the resin, for example, diallylphthalate resins andderivatives thereof, polypropylene chloride and the like, can besuitably used according to use, because they can be polymerized with theabove-mentioned compound having an ethylenically-unsaturated bond. As abinder resin, one resin selected from the above-mentioned resins, or twoor more such resins in combination, can be used.

It is preferable to use these binder resins in an amount of 500 parts byweight or less, more preferably 200 parts by weight or less, for 100parts by weight of the polymerizable compound.

An increase in sensitivity and promotion of the radical polymerizationreaction can be realized by adding the above-mentioned specific infraredabsorption agent to such a radical polymerization layer.

(Other Compounds)

In the radical polymerization layer, various additives used togetherwith conventionally known light-polymerizable compounds can beappropriately used in an amount which does not detract from the effectof the present invention.

As these additives, heat polymerization inhibitors are listed. Specificexamples thereof include quinone-based and phenol-based compounds suchas hydroquinone, pyrogallol, p-methoxyphenol, catechol, β-naphthol,2,6-di-t-butyl-p-cresol and the like, and these compounds are used in anamount of 10 parts by weight, preferably from 0.01 to 5 parts by weightfor 100 parts by weight of the total amount of the polymerizablecompound having an ethylenically unsaturated bond and the binder resin.

As a compound which can be added as an oxygen quencher,N,N-dialkylaniline derivatives such as compounds described in U.S. Pat.No. 4,772,541, column 11, line 58 to column 12, line 35, and the likeare listed.

Further, for improving film quality, plasticizers can be used. Examplesinclude exemplified phthalates, trimellitates, adipates, other saturatedor unsaturated carboxylates, citrates, epoxidated soy bean oil,epoxidated linseed oil, stearic epoxys, orthophosphates, phosphates,glycol esters and the like.

As an additive for generating an acid and promoting decomposition of theradical generator during heating, co-use of an acid generator is alsopreferable. As this acid generator, those described in detail inexplanation of the acid crosslinking layer, described below, can beused.

The above-mentioned components can be selected appropriately, dissolvedin a suitable solvent, and applied on the substrate to form the radicalpolymerization layer, and the amount applied is preferably from about0.01 to 5.0 g/m² after drying.

When the radical polymerization layer is used as a recording layer, anovercoating layer which manifests oxygen impermeability may also beprovided adjacent to the radical polymerization layer, for preventingpolymerization inhibition by oxygen. As the raw material of theovercoating layer, water-soluble resins such as polyvinyl alcohol,carboxymethylcellulose, hydroxyethylcellulose, methylcellulose,polyvinylpyrrolidone and the like are preferable, and the film thicknessthereof is suitably from about 0.2 to 3 μm.

A dye or pigment which does not absorb light from a light source usedfor recording may be added to the overcoating layer as a filter agent,if necessary.

<Acid Crosslinking Layer>

The acid crosslinking layer in the present invention contains a compoundwhich generates an acid due to light or heat (hereinafter, referred toas an acid generator) and a compound which can crosslink using thegenerated acid as a catalyst (hereinafter, referred to as a crosslinkingagent) and, further, a binder polymer which can react with thecrosslinking agent in the presence of the acid, for forming the layercontaining these compounds. In this acid crosslinking layer, acidgenerated by decomposition of the acid generator when irradiated withlight or heat promotes action of the crosslinking agent, and a strongcrosslinking structure is formed between crosslinking agents or betweenthe crosslinking agent and a binder polymer. Resultantly,alkali-solubility decreases, leading to insolubility in a developingagent.

As the acid crosslinking agent layer having such a property, knownlayers having the same property can be used. For example, there arelisted layers composed of a radiation-sensitive composition containing aresol resin, novolak resin, latent Brønsted acid, and infraredabsorption agent. Here, “latent Brønsted acid” indicates a precursorwhich is decomposed to form a Brønsted acid, and is a compound havingproperties of both the acid generator and the acid crosslinking agent inthe present invention. A Brønsted acid is believed to catalyze amatrix-formation reaction between a resol resin and a novolak resin. AsBrønsted acids suitable for this purpose, trifluoromethanesulfonic acidand hexafluorophosphonic acid are exemplified.

Further, ionic latent Brønsted acids are preferable. Examples thereofinclude onium salts, particularly, iodonium, sulfonium, phosphonium,selenonium, diazonium and arsonium salts. Nonionic latent Brønsted acidscan also be suitably used, and the following compounds: RCH₂X, RCHX₂,RCX₃, R(CH₂X)₂ and R(CH₂X)₃ (wherein, X represents Cl, Br, F, CF₃, orSO₃, and R represents an aromatic group, an aliphatic group or a bondedbody of an aromatic group and an aliphatic group) are listed.

Furthermore, a recording layer containing an acid-crosslinkable compounddescribed in JP-A 11-95415 and a binding agent having high molecularweight are also listed as suitable examples. This is a photosensitivelayer containing: a compound which can generate an acid when irradiatedwith an active beam, for example, salts of diazonium, phosphonium,sulfonium, iodonium and the like, organic halogen compounds,orthoquinone-diazidesulfonyl chloride, and organic metal/organic halogencompounds; and a compound having at least one bond which can crosslinkin the presence of the above-mentioned acid, for example, an aminocompound having at least two of alkoxymethyl groups, methylol groups,acetoxymethyl groups and the like as functional groups, at leasttwo-substituted aromatic compounds having an alkoxy methyl group,methylol group, acetoxymethyl group or the like as a functional group,resol resins and furan resins, acrylic resins synthesized from specificmonomers, and the like.

The acid crosslinking layer of the present invention contains an acidgenerator, crosslinking agent and binder polymer, and other components.Next, these compounds will be illustrated.

(Acid Generator)

In the present invention, the compound which generates acid due to lightor heat (acid generator) refers to a compound which is decomposed togenerate acid by irradiation with infrared light or heating to 100° C.or more.

As the acid generated, a strong acid having a pKa of 2 or less, such assulfonic acid, hydrochloric acid and the like, is preferable.

As the acid generator suitably used in the present invention, oniumsalts such as iodonium salts, sulfonium salts, phosphonium salts,diazonium salts and the like are listed. Specifically, compoundsdescribed in U.S. Pat. No. 4,708,925 and JP-A No. 7-20629 are listed.Particularly, iodonium salts, sulfonium salts and diazonium saltscontaining a sulfonate ion as a counter ion are preferable. As thediazonium salt, diazonium compounds described in U.S. Pat. No.3,867,147, diazonium compounds described in U.S. Pat. No. 2,632,703 anddiazo resins described in JP-A Nos. 1-102456 and 1-102457 are alsopreferable. Benzyl sulfonates described in U.S. Pat. Nos. 5,135,838 and5,200,544 are also preferable. Further, active sulfonates and disulfonylcompounds described in JP-A Nos. 2-100054, 2-100055 and 8-9444 are alsopreferable. Additionally, s-triazines substituted with a halo alkyl,described in JP-A No. 7-271029 are also preferable.

These acid generators are added into an acid crosslinking layer in aproportion of from 0.01 to 50% by weight based on the total weight ofsolid components in the acid crosslinking layer, preferably from 0.1 to40% by weight, and more preferably from 0.5 to 30% by weight. If theaddition amount is less than 0.01% by weight, an image may not beobtained. If the addition amount is over 50% by weight, staining mayoccur at non-image parts in printing.

These compounds may be used alone or in a combination of two or more.Since the acid generators listed above can be decomposed also byirradiation with ultraviolet light, if a recording layer having such aform is used, an image can be recorded not only by irradiation withinfrared light but also by irradiation with ultraviolet light.

(Crosslinking Agent)

The crosslinking agent which can be used in the acid crosslinking layerof the present invention is not particularly restricted providing it isa compound which can be crosslinked by action of an acid, and preferablyused are phenol derivatives of the following general formula (5)(hereinafter, referred to as a low molecule phenol derivatives, asappropriate), poly-nuclear type phenolic crosslinking agents having inthe molecule thereof three or more phenol rings which have two or threehydroxymethyl groups on the rings, of the following general formula (6),and mixtures of the above-mentioned low molecule phenol derivative withthe poly-nuclear type phenolic crosslinking agent and/or a resol resin,and the like.

In this formula, Ar¹ represents an aromatic hydrocarbon ring optionallyhaving a substituent. R¹ and R² may be the same or different. R³represents a hydrogen atom or a hydrocarbon group having 12 or lesscarbon atoms. m represents an-integer from 2 to 4. n represents aninteger from 1 to 3. X represents a divalent connecting group. Yrepresents a mono-valent to tetra-valent connecting group having theabove-mentioned partial structure, or a functional group carrying ahydrogen atom at an end. Z is not present if Y is an end group, orrepresents a mono-valent to tetra-valent connecting group or functionalgroups present depending on the number of connecting groups of Y.

In this formula, A represents an r-valent hydrocarbon connecting grouphaving 1 to 20 carbon atoms, and r represents an integer from 3 to 20. prepresents an integer from 2 to 3.

Phenol derivatives of the general formula (5) are described in detail inJapanese Patent Application No. 11-352210, paragraph nos. [0098] to[0155], submitted by the present applicant. Poly-nuclear type phenoliccrosslinking agents having in the molecule three or more phenol ringshaving 2 or 3 hydroxymethyl groups on the rings, of the general formula(6), are also described in detail in the same specification, inparagraph nos. [0156] to [0165].

These crosslinking agents may be used alone or in a combination of twoor more.

In the present invention, the crosslinking agent is used in an additionamount of from 5 to 70% by weight, preferably from 10 to 65% by weightbased on the total weight of solid components in the acid crosslinkinglayer. If the addition amount of the crosslinking, agent is less than 5%by weight, the film strength of an image part when an image is recordedwill deteriorate, and if over 70% by weight, stability in storage willnot be preferable.

As the binder polymer which can be used in the acid crosslinking layerof the present invention, polymers having on a side chain or main chainan aromatic hydrocarbon ring to which a hydroxyl group or alkoxy groupis directly bonded are listed. As the alkoxy group, those having 20 orless carbon atoms are preferable from the standpoint of sensitivity. Asthe aromatic hydrocarbon ring, a benzene ring, naphthalene ring oranthracene ring is preferable from the standpoint of availability of rawmaterials. These aromatic hydrocarbon rings may have other substituentsthan the hydroxyl group or alkoxy group, for example, substituents suchas halogen groups, cyano groups and the like. However, from thestandpoint of sensitivity, it is preferable that the aromatichydrocarbon group has no other substituent than the hydroxyl group oralkoxy group.

In the present invention, a binder polymer which can be suitably used isa polymer having a constituent unit of the following general formula(7), or a phenol resin such as a novolak resin or the like.

In this formula, Ar² represents a benzene ring, naphthalene ring oranthracene ring. R⁴ represents a hydrogen atom or methyl group. R⁵represents a hydrogen atom or alkoxy group having 20 or less carbonatoms. X¹ represents a single bond, or a di-valent connecting grouphaving 0 to 20 carbon atoms and containing one or more atoms selectedfrom C, H, N, O and S. k represents an integer from 1 to 4.

In the present invention, though a homopolymer composed solely of aconstituent unit of the general formula (7) may be used as the binderpolymer, a copolymer having a constituent unit derived from anotherknown monomer together with this specific constituent unit may also beused.

The proportion of the constituent unit of the general formula (7)contained in the copolymer obtained therefrom is preferably from 50 to100% by weight, and further preferably from 60 to 100% by weight.

The polymer used in the present invention has a weight-average molecularweight of preferably 5,000 or more, further preferably from 10,000 to300,000, and a number-average molecular weight of preferably 1,000 ormore, further preferably from 2,000 to 250,000. The degree ofpolydispersity (weight-average molecular weight/number-average molecularweight) is preferably 1 or more, and further preferably from 1.1 to 10.

These polymers may be any of a random polymer, block polymer, graftpolymer and the like, and a random polymer is preferable.

Next, the novolaks will be described. As a novolak resin suitably usedin the present invention, phenol novolaks, o-, m- and p-cresol novolaks,and copolymers thereof, and novolaks obtained by utilizing phenolssubstituted with a halogen atom, alkyl group or the like, are listed.

The novolak resin has a weight-average molecular weight of preferably1,000 or more, further preferably from 2,000 to 20,000, and anumber-average molecular weight of preferably 1,000 or more, furtherpreferably from 2,000 to 15,000. The degree of polydispersity ispreferably 1 or more, and further preferably from 1.1 to 10.

Use of a polymer having a heterocyclic ring that has an unsaturated bondin the ring as the binder polymer is also a preferable embodiment.

Here, the heterocyclic ring means a ring containing one or moreheteroatoms other than carbon, as atoms constituting the ring system. Asheteroatoms used, nitrogen atoms, oxygen atoms, sulfur atoms and siliconatoms are preferable. It is believed that by use of a polymer havingsuch a heterocyclic group, a reaction tends to occurchemical-structurally, due to function of a lone pair existing in thisheterocyclic ring, to thereby form a film having excellent printingendurance.

The binder polymer as described above used in the present invention maybe used alone or in a combination of two or more. This polymer is addedin a proportion of from 20 to 95% by weight based on the total weight ofsolid components in an acid crosslinking layer, and preferably from 40to 90% by weight. If the addition amount is less than 20% by weight,strength of image parts will be deficient when images are formed. On theother hand, if the addition amount is over 95% by weight, images willnot be formed.

Also, in this acid crosslinking layer, sensitivity can be improved byinclusion of the infrared absorption agent.

In forming this acid crosslinking layer, various additives such as asurfactant and the like can be used therewith for purposes of improvingapplicability and film quality and the like.

As the positive recording layer, interaction releasing systems (heatsensitive positive), acid catalyst decomposition systems, andpolarity-conversion systems are listed. These are described below inthis order.

<Interaction Releasing System (Heat Sensitive Positive)>

The interaction releasing system is constituted of a water-insolublepolymer, an alkaline water-soluble polymer, and an infrared absorptionagent.

Now, the alkali-soluble polymer compound which can be used in a positiverecording layer includes homopolymers containing an acidic group on themain chain and/or side chain of the polymer, copolymers thereof, andmixtures thereof.

Among these, those having an acidic group exemplified in the following(1) to (6) on the main chain and/or side chain of the polymer arepreferable from the standpoint of solubility in an alkaline developingsolution, and from the standpoint of manifestation ofdissolution-suppressing ability.

(1) Phenol group (—Ar—OH)

(2) Sulfonamide group (—SO₂NH—R)

(3) Substituted sulfonamide-based acid group (hereinafter, referred toas “active imide group”) [—SO₂NHCOR, —SO₂NHSO₂R, —CONHSO₂R]

(4) Carboxyl group (—CO₂H)

(5) Sulfonic group (—SO₃H)

(6) Phosphoric group (—OPO₃H₂)

In the above (1) to (6), Ar represents a di-valent aryl connecting groupoptionally having a substituent, and R represents a hydrocarbon groupoptionally having a substituent.

Among alkaline water-soluble polymers having an acidic group selectedfrom the above-mentioned (1) to (6), alkaline water-soluble polymershaving (1) a phenol group, (2) a sulfonamide group and (3) an activeimide group are most preferable from the standpoints of solubility inthe alkaline developing solution, developing latitude, and sufficientensuring of film strength.

As alkaline water-soluble polymers having an acidic group selected fromthe above-mentioned (1) to (6), the following polymers are exemplified.

(1) As an alkaline water-soluble polymer having a phenol group, forexample, novolak resins such as polycondensates of phenol withformaldehyde; polycondensates of m-cresol with formaldehyde;polycondensates of p-cresol with formaldehyde; polycondensates ofm-/p-mixed cresol with formaldehyde; polycondensates of phenol, cresol(may be m-, p- or m-/p-mixed type) and formaldehyde, and the like; andpolycondensates of pyrogallol with acetone are listed. Further,copolymers obtained by copolymerizing a compound having a phenol groupon the side chain are listed. Alternatively, copolymers obtained bycopolymerizing a compound having a phenol group on the side chain canalso be used.

As the compound having a phenol group, acrylamides, methacrylamides,acrylates, methacrylates, hydroxystyrenes and the like are listed.

The alkaline water-soluble polymer preferably has a weight-averagemolecular weight from 5.0×10² to 2.0×10⁴ and a number-average molecularweight from 2.0×10² to 1.0×10⁴, from the standpoint of image-formationproperty. These polymers may be used alone, or in a combination of twoor more. In the case of a combination, a polycondensate of phenol withformaldehyde having as a substituent an alkyl group having 3 to 8 carbonatoms, such as a polycondensate of t-butylphenol with formaldehyde and apolycondensate of octylphenol with formaldehyde as described in U.S.Pat. No. 4,123,279, alkaline water-soluble polymers having a phenolstructure having an electron attractive group on an aromatic ring asdescribed in Japanese Patent Application No. 11-47019 submittedpreviously by the present inventor, and the like may be used together.

(2) As the alkaline water-soluble polymer having a sulfonamide group,for example, polymers constituted, as the main constituent component, ofa minimum constituent unit derived from a compound having a sulfonamidegroup are listed. As the above-mentioned compound, compounds having inthe molecule one or more sulfonamide-groups in which at least onehydrogen atom is bonded to a nitrogen atom and one or more polymerizableunsaturated bonds are: listed. Among others, low molecular weightcompounds having in the molecule an acryloyl group, allyl group orvinyloxy group and a substituted or mono-substituted aminosulfonyl groupor a substituted sulfonylimino group are preferable. For example,compounds of the following general formulae 8 to 12 are listed.

In these formulae, each of X¹ and X² independently represents —O— or—NR²⁷—. Each of R²¹ and R²⁴ independently represents a hydrogen atom or—CH₃. Each of R²², R²⁵, R²⁹, R³² and R³⁶ independently represents analkylene group, a cycloalkylene group, an arylene group or an aralkylenegroup, having 1 to 12 carbon atoms and optionally having a substituent.Each of R²³, R²⁷ and R³³ independently represents a hydrogen atom or analkyl group, a cycloalkyl group, an aryl group or an aralkyl group,having 1 to 12 carbon atoms and optionally having a substituent.Further, each of R²⁶ and R³⁷ independently represents an alkyl group, acycloalkyl group, an aryl group or an aralkyl group, having 1 to 12carbon atoms and optionally having a substituent. Each of R²⁸, R³⁰ andR³⁴ independently represents a hydrogen atom or —CH₃. Each of R³¹ andR³⁵ independently represents a single bond, or an alkyl group, acycloalkylene group, an arylene group or an aralkylene group, having 1to 12 carbon atoms and optionally having a substituent. Each of Y³ andY⁴ independently represents a single bond, or —CO—.

Among compounds of the general formulae 8 to 12, m-aminosulfonylphenylmethacrylate, N-(p-aminosulfonylphenyl)methacrylamide,N-(p-aminosulfonylphenyl)acrylamide and the like can be suitably used inthe positive planographic printing material of the present invention.

(3) As the alkaline water-soluble polymer having an active imide group,for example, polymers constituted, as the main constituent component, ofa minimum constituent unit derived from a compound having an activeimide group are listed. As the above-mentioned compound, compoundshaving in the molecule one or more active imide groups of the followingstructural formula and one or more polymerizable unsaturated bonds arelisted.

Specifically, N-(p-toluenesulfonyl)methacrylamide,N-(p-toluenesulfonyl)acrylamide and the like can be suitably used.

(4) As the alkaline water-soluble polymer having a carboxyl group, forexample, polymers constituted, as the main constituent component, of aminimum constituent unit derived from a compound having in the moleculeone or more carboxyl groups and one or more polymerizable unsaturatedgroups are listed.

(5) As the alkaline water-soluble polymer having a sulfonic group, forexample, polymers constituted, as the main constituent component, of aminimum constituent unit derived from a compound having, in themolecule, one or more sulfonic groups and one or more polymerizableunsaturated groups are listed.

(6) As the alkaline water-soluble polymer having a phosphate group, forexample, polymers constituted, as the main constituent component, of aminimum constituent unit derived from a compound having in the moleculeone or more phosphate groups and one or more polymerizable unsaturatedgroups are listed.

The minimum constituent unit having an acidic group selected from theabove-mentioned (1) to (6) constituting an alkaline water-solublepolymer to be used in the positive recording layer is not necessarilyrestricted to one kind specifically, and those obtained bycopolymerizing two or more minimum constituent units having the sameacidic group or two or more minimum constituent units having differentacidic groups can also be used.

In the above-mentioned polymers, compounds having an acidic groupselected from (1) to (6) to be copolymerized are contained in thecopolymer preferably in an amount of 10 mol % or more, and morepreferably 20 mol % or more. If less than 10 mol %, there is a tendencythat developing latitude can not be sufficiently improved.

<Acid Catalysis Decomposition System>

A chemical amplification layer is preferably formed on an exposuresurface of an uppermost layer of the recording layer, and contains, asan essential component, a compound which generates acid due to action oflight or heat (acid generator), and a compound which manifests cleavageof a chemical bond using the generated acid as a catalyst, to increasesolubility in the alkaline developing solution (an acid-decomposablecompound).

The chemical amplification layer may further contain a polymer compoundwhich is a binder component for forming this layer, or theabove-mentioned acid-decomposable compound itself may be a polymercompound which performs the function of a binder component, or aprecursor thereof.

[Acid-Decomposable Compound]

In the present invention, the compound which manifests cleavage of achemical bond using the acid as a catalyst to increase solubility in thealkaline developing solution is, in other words, a compound having inthe molecule a bonding group which can be decomposed by an acid. As sucha compound, those described as “(b) compound having at least one bonddecomposable by an acid” in-JP-A No. 9-171254 can be used. As the bonddecomposable by an acid, for example, —(CH₂CH₂O)_(n)— groups (nrepresents an integer from 2 to 5) and the like are preferably listed.

Among such compounds, compounds of the following general formula (13)are preferably used from the standpoints of sensitivity and developingproperty.

In this formula, each of R, R¹ and R² represents a hydrogen atom, alkylgroup having 1 to 5 carbon atoms, alkoxy group having 1 to 5 carbonatoms, sulfo group, carboxyl group or hydroxyl group; each of p, q and rrepresents an integer from 1 to 3; and each of m and n represents aninteger from 1 to 5.

In the above-mentioned general formula (13), alkyl groups represented byR, R¹ and R² may be linear or branched, and examples thereof include anethyl group, propyl group, isopropyl group, butyl group, tert-butylgroup, pentyl group and the like. As alkoxy groups, for example, amethoxy group, ethoxy group, propoxy group, isopropoxy-group, butoxygroup, tert-butoxy group, pentoxy group and the like are listed. Sulfogroups and carboxyl groups include salts thereof. Among compounds of thegeneral formula (13), those in which m and n are 1 or 2 are particularlypreferable. Compounds of the general formula (13) can be synthesized bya known method.

In addition, as an acid-decomposable compound which can be used with thepresent invention, there are listed compounds having a C—O—C bonddescribed in JP-A Nos. 48-89603, 51-120714, 53-133429, 55-12995,55-126236 and 56-17345; compounds having a Si—O—C bond described in JP-ANos. 60-37549 and 60-121446; and other acid-decomposable compoundsdescribed in JP-A Nos. 60-3625 and 60-10247. Further listed arecompounds having a Si—N bond described in JP-A No. 62-222246, carbonatesdescribed in JP-A No.62-251743, orthocarbonates described in JP-A No.62-209451, orthotitanates described in JP-A No. 62-280841,orthosilicates described in JP-A No. 62-280842, acetals, ketals andorthocarbonates described in JP-A Nos. 63-010153, 9-171254, 10-55067,10-111564, 10-87733, 10-153853, 10-228102, 10-268507, 10-282648 and10-282670, EP-0884547A1, and compounds having a C—S bond described inJP-A No. 62-244038.

Among the above-mentioned acid-decomposable compounds, particularlycompounds having a C—O—C bond, compounds having a Si—O—C bond,orthocarbonates, acetals, ketals and silyl ethers described in JP-A Nos.53-133429,56-17345, 60-121446, 60-37549,62-209451, 63-010153, 9-171254,10-55067, 10-111564, 10-87733, 10-153853, 10-228102, 10-268507,10-282648 and 10-282670, and EP-0884547A1 are preferable.

Among these acid-decomposable compounds, polymer compounds which have inthe main chain a repeating acetal or ketal part and of which solubilityin an alkaline developing solution is increased by the generated acidare preferably used.

These acid-decomposable compounds may be used alone or in a combinationof two or more. Regarding the addition amount, these compounds are addedinto the chemical amplification layer in a proportion of from 5 to 70%by weight based on the total weight of solid components in the layer,preferably from 10 to 50% by weight, and more preferably from 15 to 35%by weight. If the addition amount is less than 5% by weight, staining ofnon-image parts tends to occur, and if over 70% by weight, film strengthin image parts becomes insufficient. That is, both these cases are notpreferable.

<Polarity-Conversion System>

A polarity-conversion material which changes from lipophilic tohydrophilic when heated is a material which varies from a state in whichaffinity, such as swelling or dissolution or the like, is not manifestedfor water at normal temperature to a state in which affinity ismanifested for water. This variation may be or may not be accompanied bya chemical reaction. However, a variation accompanied by a chemicalreaction is preferable since the extent of conversion of polarity islarge. As such a polarity-conversion reaction, a reaction that generatesa hydrophilic group by heat is exemplified. As a hydrophilicsubstituent, acidic groups such as a phosphonic group, sulfonic group,carboxyl group, sulfonamide, phenol and the like, a hydroxyl group,amino groups and the like, and onium salts such as an ammonium salt andthe like are listed. Reactions are preferable in which such asubstituent is manifested by action of heat. As such apolarity-conversion material, carboxylates described in JP-A No. 7-186562, photochromic compounds described in JP-A Nos. 9-240148, 4-44895,8-3463 and 8-156401, inorganic compounds described in JP-A No.51-115101, and compounds which can generate a sulfonic acid described inJP-A No. 10-282672 are listed. Further, protective groups that generatethe above-mentioned hydrophilic group are also used suitably. As suchprotective groups, those described in “Protective Groups in OrganicSynthesis” (Greene, Theodra W. and Wuts, Peter G. M., Wiley-IntersciencePublication), and “Protecting Groups” (Philip J. Kocienski, GeorgeThieme Verlag Stuttgart) are listed. These may have high molecularweight or low molecular weight.

The reaction temperature is preferably from 80° C. to 300° C.,particularly preferably from 120° C. to 200° C. When the reactiontemperature is lower, storage stability lowers, and when the reactiontemperature is higher, sensitivity lowers.

[Other Components]

In the image-formation material of the present invention, variousadditives can be further added, if necessary. For example, addition ofother onium salts, aromatic sulfone compounds, aromatic sulfonatecompounds, poly-functional amine compounds and the like is preferablesince a function to inhibit dissolution of an alkaline water-solublepolymer into a developing solution can be improved when such compoundsare added.

As the above-mentioned onium salts: diazonium salts, ammonium salts,phosphonium salts, iodonium salts, sulfonium salts, selenonium salts,arsonium salts and the like are listed. The onium salt is preferablyadded in an amount of from 1 to 50% by weight based on the total amountof solid components constituting the image-formation material, morepreferably from 5 to 30% by weight, and particularly preferably from 10to 30% by weight.

Also, for the purpose of further improving sensitivity, cyclic acidanhydrides, phenols, and organic acids can be used together therewith.As a cyclic acid anhydride, phthalic anhydride, tetrahydrophthalicanhydride, hexahydrophthalic anhydride,3,6-endoxy-Δ4-tetrahydro-phthalic anhydride, tetrachlorophthalicanhydride, maleic anhydride, chloromaleic anhydride, α-phenylmaleicanhydride, succinic anhydride, pyromellitic anhydride and the likedescribed in U.S. Pat. No. 4,115,128 can be used. As a phenol, bisphenolA, p-nitrophenol, p-ethoxyphenol, 2,4,4′-trihydroxybenzophenone,2,3,4-trihydroxybenzophenone, 4-trihydroxybenzophenone,4,4′,4″-trihydroxytriphenylmethane,4,4′,3″,4″-tetrahydroxy-3,5,3′,5′-tetramethyltriphenylmethane and thelike are listed. Further, as an organic acid, sulfonic acids, sulfinicacids, alkylsulfuric acids, phosphonic acids, phosphates and carboxylicacids and the like described in JP-A Nos. 60-88942 and 2-96755 and thelike-are listed.

The proportion of the above-mentioned cyclic acid anhydrides, phenolsand organic acids present in the image-formation material is preferablyfrom 0.05 to 20% by weight, more preferably from 0.1 to 15% by weight,and particularly preferably from 0.1 to 10% by weight.

Further, in addition to these, epoxy compounds, vinyl ethers, phenolcompounds having a hydroxymethyl group and phenol compounds having analkoxy methyl group described in JP-A No. 8-276558, and crosslinkablecompounds having an alkali disolution-suppressing action described inJP-A No. 11-160860, submitted previously by the present inventor, andthe like can be appropriately added, according to objectives.

Further, in the printing plate of the present invention, nonionicsurfactants as described in JP-A Nos. 62-251740 and 3-208514, andampholytic surfactants as described in JP-A Nos. 59-0121044 and 4-13149can be added for widening processing stability under developingconditions.

In the printing plate of the present invention, a printout agent forobtaining a visible image directly after heating by exposure, and a dyeor pigment as an image coloring agent can be added.

As the printout agent, there are typically listed combinations oforganic dyes which can form a salt with a compound that releases an acidwhen heated by exposure (optical acid releasing agent); Specificexamples include a combination of o-naphthoquinonediazide-4-sulfonicacid halogenide with a salt-forming organic dye described in JP-A Nos.50-36209 and 53-8128, and a combination of a trihalomethyl group with asalt-forming organic dye described in JP-A Nos. 53-36223, 54-74728,60-3626, 61-143748, 61-151644 and 63-58440. As such a trihalomethylgroup, oxazole-based compounds and triazine-based compounds areexemplified, and both of these are excellent in stability with the lapseof time, and give a clear printout image.

As a coloring agent for an image, other dyes can be used in addition tothe salt-forming organic dye described above. Oil-soluble dyes and basicdyes are listed as suitable dyes, including salt-forming organic dyes.Specifically, Oil Yellow # 101, Oil Yellow # 103, Oil Pink #312, OilGreen BG, Oil Blue BOS, Oil Blue #603, Oil Black BY, Oil Black BS, OilBlack T-505 (these are manufactured by Orient Chemical Industry Co.),Victoria Blue, Crystal Violet (CI42555), Methyl Violet (CI42535), EthylViolet, Rhodamine B (CI145170B), Malachite Green (CI42000), MethyleneBlue (CI52015) and the like are listed. Dyes described in JP-A No.62-293247 are particularly preferable. These dyes can be added to aprinting material in a proportion of from 0.01 to 10% by weight based onthe total amount of solid components in the printing material, andpreferably from 0.1 to 3% by weight.

Further, a plasticizer may be added to the printing plate material ofthe present invention, for imparting flexibility of a film and the like,if necessary. For example, butylphthalyl, polyethylene glycol, tributylcitrate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate,dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctylphosphate, tetrahydrofurfuryl oleate, oligomers and polymers of acrylicacid and methacrylic acid, and the like are used.

A recording layer coating solution containing the image-formationmaterial of the present invention, or coating solution components of adesired layer such as a protective layer or the like, can be dissolvedin a solvent and applied to a suitable substrate, to produce animage-formation material. Examples of the solvent herein used include,but are not limited to, ethylene dichloride, cyclohexanone, methyl ethylketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether,1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propylacetate, dimethoxyethane, methyl lactate, ethyl lactate,N,N-dimethylacetoamide, N,N-dimethylformamide, tetramethylurea,N-methylpyrrolidone, dimethylsulfoxide, sulfolane, γ-butyrolactone,toluene, water and the like. These solvents can be used alone or inadmixture. The concentration of the above-mentioned components (allsolid components including additive) in the solvent is preferably from 1to 50% by weight. The coating amount after drying (solid component) onthe substrate differs depending on use, and is preferably from 0.5 to5.0 g/m², in general, for a photosensitive printing plate.

As the coating method., various methods can be used. For example, barcoater coating, rotation coating, spray coating, curtain coating, dipcoating, air knife coating, blade coating, roll coating and the like arelisted. When the coating amount decreases, apparent sensitivityincreases but the film property of the recording layer decreases.

Surfactants for improving coatability, for example, fluorine-basedsurfactants as described in JP-A No. 62-170950, can be added to therecording layer coating solution using the image-formation material inthe present invention. A preferable addition amount is from 0.01 to 1%by weight, further preferably from 0.05 to 0.5% by weight, based on thewhole printing plate material.

The substrate used for the image-formation material of the presentinvention is a dimensionally stable plate., and examples thereof includepaper, paper laminated with a plastic (e.g., polyethylene,polypropylene, polystyrene and the like), metal plates (e.g., aluminum,zinc, copper and the like), plastic films (e.g., cellulose diacetate,cellulose triacetate, cellulose propionate, cellulose butyrate,cellulose acetate butyl ate, cellulose nitrate, polyethyleneterephthalate, polyethylene, polystyrene, polypropylene, polycarbonate,polyvinyl acetal and the like), paper laminated or deposited with metalsas described above, and plastic films and the like.

As the substrate used in the image-formation material of the presentinvention, polyester films and aluminum plates are preferable. Of these,an aluminum plate, which has excellent dimension stability and isrelatively cheap, is particularly preferable. A suitable aluminum plateis a pure aluminum plate or an alloy plate containing aluminum as themain component and containing trace amounts of hetero elements. Further,a plastic film laminated or deposited with aluminum may be permissible.As the hetero elements contained in the aluminum alloy, silicon, iron,manganese, copper, magnesium, chromium, bismuth, nickel, titanium andthe like are listed. The content of hetero elements in the alloy is atmost 10% by weight. A particularly suitable aluminum in the presentinvention is pure aluminum. However, since completely pure aluminum isdifficult to produce from the refining technology standpoint, traceamounts of hetero elements may be contained. Thus, the aluminum plateapplied to the present invention is not specified regarding composition,and aluminum plates made of conventionally-known and used raw materialscan be utilized appropriately. The aluminum plate used in the presentinvention has a thickness of about from 0.1 mm to 0.6 mm, preferablyfrom 0.15 mm to 0.4 mm, and particularly preferably from 0.2 mm to 0.3mm.

Prior to roughening of the aluminum plate, there is conducted adegreasing treatment with, for example, a surfactant, organic solvent,alkaline aqueous solution or the like, for removing a rolling oil fromthe surface, if necessary.

The treatment for roughening the surface of the aluminum plate may beconducted by various methods and may be, for example, effected by amethod of mechanical roughening, a method of dissolving and rougheningthe surface electrochemically, or a method of selectively dissolving thesurface chemically. As the mechanical method, known methods such as aball polishing method, brush polishing method, blast polishing method,buff polishing method or the like can be used. As the electrochemicalroughening method, there are methods conducted by alternating current ordirect current in hydrochloric acid or nitric acid electrolytes.Further, a method obtained by combining both of these can also beutilized, as disclosed in JP-A No. 54-63902.

An aluminum plate thus surface-roughened is subjected to an alkalietching treatment and neutralization treatment if necessary, and thensubjected to an anodizing treatment for enhancing water-retainingproperty and abrasion resistance of the surface, if desired. As theelectrolyte used in the anodizing treatment of the aluminum plate, useof various electrolytes for forming a porous oxide film is possible. Ingeneral, sulfuric acid, phosphoric acid, oxalic acid, chromic acid or amixed acid thereof is used. The concentration of these electrolytes isappropriately selected depending on the kind of electrolyte.

Treatment conditions of anodizing cannot be generally specified sincethey change variously depending on electrolytes used. However, ingeneral, it is appropriate that concentration of electrolytes is from 1to 80% by weight, liquid temperature is from 5 to 70° C., currentdensity is from 5 to 60 A/dm², voltage is from 1 to 100 V, andelectrolysis time is from 10 seconds to 5 minutes.

If the amount of an anodized film is less than 1.0 g/m², printingendurance will be insufficient, and non-image parts on the planographicprinting plate will be easily scratched, leading to a tendency ofso-called “scratch staining” in which ink adheres to scratched parts inprinting.

After performing the anodizing treatment, a hydrophilization treatmentis performed on the surface of the aluminum, if necessary. As thehydrophilization treatment used in the present invention, there is analkali metal silicate (for example, sodium silicate aqueous solution)method as disclosed in U.S. Pat. Nos. 2,714,066, 3,181,461, 3,280,734and 3,902,734. In this method, the substrate is immersed in a sodiumsilicate aqueous solution, or electrolyzed. In addition, there aremethods of treatment with potassium zirconate fluoride, disclosed inJP-B No. 36-22063, or polyvinyl phosphonic acid as disclosed in U.S.Pat. Nos. 3,276,868, 4,153,461 and 4,689,272.

The image-formation material of the present invention comprises asubstrate carrying thereon a recording layer provided with theimage-formation layer of the present invention. If necessary, a primerlayer can be provided therebetween.

As the primer layer components, various organic compounds can be usedand, for example, selected from carboxymethylcellulose, dextrin, gumArabic; phosphonic acids having an amino group such as2-aminoethylphosphonic acid and the like; organic phosphonic acids suchas phenylphosphonic acid, naphthylphosphonic acid, alkylphosphonic acid,glycerophosphonic acid, methylenediphosphonic acid, ethylenediphosphonic acid and the like optionally having a substituent; organicphosphoric acid such as phenylphosphoric acid, naphthylphosphoric acid,alkylphosphoric acid, glycerophosphoric acid and the like optionallyhaving a substituent; organic phosphinic acids such as phenylphosphinicacid, naphthylhphosphinic acid, alkylphosphinic acid, glycerophosphinicacid and the like optionally having a substituent; amino acids such asglycine, β-alanine and the like; and hydrochlorides of amines having ahydroxy group such as a hydrochloride of triethanolamine and the like;and two or more of these may be mixed for use.

On a planographic printing plate produced as described above, image-wiseexposure and developing treatment are performed as usual.

As the light source of an active beam used in image-wise exposure, solidlasers and semiconductor lasers radiating infrared light havingwavelengths from 720 to 1200 nm and the like are listed.

In the present invention, light sources having emitting wavelengths fromthe near-infrared range to the infrared range are preferable, and solidlasers and semiconductor lasers are particularly preferable.

As a development solution and replenishment solution for theimage-formation material of the present invention, conventionally knownalkaline aqueous solutions can be used. For example, inorganic alkalisalts are listed, such as sodium silicate, potassium silicate, sodiumtertiary phosphate, potassium tertiary phosphate, ammonium tertiaryphosphate, sodium secondary phosphate, potassium secondary phosphate,ammonium secondary phosphate, sodium carbonate, potassium carbonate,ammonium carbonate, sodium hydrogen carbonate, potassium hydrogencarbonate, ammonium hydrogen carbonate, sodium borate, potassium borate,ammonium borate, sodium hydroxide, ammonium hydroxide, potassiumhydroxide, lithium hydroxide and the like. Further, organic alkaliagents are also used such as monomethylamine, dimethylamine,trimethylamine, monoethylamine, diethylamine, triethylamine,monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine,monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine,diisopropanolamine, ethyleneimine, ethylenediamine, pyridine and thelike.

These alkali agents are used alone or in a combination of two or more.

Particularly preferable developing solutions among these alkali agentsare silicate aqueous solutions of sodium silicate, potassium silicateand the like. The reason for this is that developing property can becontrolled by the concentrations and the ratio of silicon oxide SiO₂,which is a component of a silicate, to an alkali metal oxide M₂O. Alkalimetal silicates as described in JP-A No. 54-62004 and JP-B No. 57-7427are effectively used.

Further, when development is effected using an automatic developingmachine, it is known that a large number of photosensitive plates can betreated without changing the developing solution in a developing tankfor a long period of time, by adding an aqueous solution (replenishmentsolution) having higher alkali strength than the developing solution tothe developing solution. This replenishment method is also preferablyapplied in this invention. Various surfactants and organic solvents canbe added to the developing solution and replenishment solution, ifnecessary, for purposes of enhancing promotion/suppression of thedeveloping solution, dispersion of development residue and ink-affinityof image parts of the printing plate. As preferable surfactants,anionic, cationic, nonionic and ampholytic surfactants are listed.

Reducing agents can also be added to the developing solution andreplenishment solution as necessary, such as hydroquinone, resorcin, andsodium salts and potassium salts and the like of inorganic acids such assulfurous acid, hydrogensulfurous acid and the like. Further, organiccarboxylic acids, defoaming agents and hard water softening agents canalso be added, if necessary.

The printing plate subjected to development treatment using theabove-mentioned developing solution and replenishment solution issubjected to post-treatment with a washing solution, a rinse solutioncontaining surfactants and the like, or a de-sensitizing solutioncontaining gum Arabic and a starch derivative. As a post-treatment whenthe image-formation material of the present invention is used for aprinting plate, these treatments can be variously combined and used.

Recently, automatic developing machines for printing plates have beenwidely used for rationalization and standardization of plate productionwork in plate production and printing industries. These automaticdeveloping machines are, in general, composed of a development sectionand a post-treatment section, and have an apparatus for transporting aprinting plate, treating solution vessels, and a spray apparatus. Adeveloping treatment therein is conducted by spraying treating solutionssucked up by pumps through spray nozzles while horizontally transportinga printing plate which has been exposed. Further, recently, there isalso known a method in which a printing plate is treated by beingimmersed and transported by a submerged guide roll in a treatingsolution vessel filled with a treatment solution. In such automatictreatment, treatment can also be conducted while replenishing areplenishment solution to the treatment solution based on treatmentamount, working time and the like.

Further, a so-called disposable treatment method in which treatment iseffected with a substantially unused treating solution can also be used.

A photosensitive planographic printing plate using the image-formationmaterial of the present invention will be described. When a planographicprinting plate obtained by image-wise exposure, development,water-washing and/or rinse and/or gum-drawing carries unnecessary imageparts (for example, a film edge trace of an original picture film andthe like), the unnecessary image parts should be eliminated. For suchelimination, a method, for example, as described in JP-B No. 2-13293, inwhich an elimination solution is applied to the unnecessary image parts,left as is for a given time, and then washed with water is preferablyused. However, a method can also be used, as described in JP-A No.59-174842, in which an active beam introduced through an optical fiberis allowed to irradiate the unnecessary image parts before development.

The planographic printing plate obtained as described above can be,after application of desensitizing gum as necessary, subjected to aprinting process. If a planograhpic printing plate having higherprinting endurance is desired, a burning treatment is performed.

When a planographic printing plate is subjected to the burningtreatment, it is preferable to conduct a treatment with a surfacesmoothing solution as described in JP-B Nos. 61-2518 and 55-28062, JP-ANos. 62-31859 and 61-159655, before the burning treatment,

As this treatment, a method in which the surface smoothing solution isapplied to the planographic printing plate using a sponge or absorbentcotton impregnated with this solution, a method in which the printingplate is immersed in a bath filled with the surface smoothing solutionto effect coating onto the plate, a method with an automatic coater, andthe like can be applied. Further, more preferable results are obtainedif, after coating, the applied amount is made uniform by a squeegee orsqueeze roller.

The amount of the surface smoothing solution applied is, in general,suitably from 0.03 to 0.8 g/m² (dry weight).

The planographic printing plate onto which the surface smoothing agenthas been applied is dried if necessary, and then heated to a hightemperature by a burning processor (for example, a burning processor:“BP-1300”, available from Fuji Photo Film Co., Ltd.) or the like. Inthis case, it is preferable that the heating temperature is from 180 to300° C. and the heating time is from 1 to 20 minutes, depending on thekinds of image-forming components.

On the planographic printing plate which has been subjected to theburning treatment, conventionally conducted treatments such as washingwith water, gum-drawing and the like can be performed appropriately ifnecessary. However, if a surface smoothing solution containing awater-soluble polymer compound or the like is used, so-calledde-sensitizing treatments such as gum drawing and the like can beomitted.

The planographic printing plate obtained by such treatments is subjectedto treatment in an offset printing machine, and used for printing alarge number of sheets.

EXAMPLES

The following examples will illustrate the present invention, but do notlimit the scope of the present invention.

[Synthesis of Infrared Absorber]

1. Synthesis of Exemplary Compound (IR-5) Included in General Formula(1)

9.5 g of p-toluenesulfonyl chloride and 18.2 g of 1H, 1H, 2H,2H-perfluorooctan-1-ol were dissolved in 50 ml of acetone. This solutionwas stirred while cooling with ice, and 5.6 g of triethylamine was addedto this dropwise over 10 minutes. This reaction solution was raised toroom temperature, the solution was stirred for 6 hours, and then pouredinto 250 ml of water. An organic layer was extracted with ethyl acetate,washed with water, and then dried over sodium sulfate. The solvent wasdistilled off under reduced pressure to obtain 24.4 g of 1H, 1H, 2H,2H-perfluorooctyl p-toluenesulfonate.

17.1 g of 1H, 1H, 2H, 2H-perfluorooctyl p-toluenesulfonate and 4.78 g of2,3,3-trimethylindolenine were mixed in a reaction vessel, and thismixture was heated at 100° C. and stirred for 1 hour. This reactionsolution was cooled to room temperature. 5.39 g ofN-(3-(anilinomethylene)-2-chloro-1-cyclohexen-1-yl)methylene)anilinehydrochloride, 60 ml of methanol and 6.13 g of acetic anhydride wasadded, and the mixture was stirred for 10 minutes while cooling withwater. 6.07 g of triethylamine was slowly added dropwise to the reactionsolution, and the mixture was stirred for 2 hours at room temperature.The reaction solution was cooled to about 0° C. A precipitate wasfiltrated, and washed with water to obtain 6.5 g of the exemplarycompound (IR-4) (λ_(max)=795 nm, ε=270,000, in methanol).

Counter ions of 5.0 g of the exemplary compound (IR-4) were substitutedby perchlorate ions by an ordinary method, to obtain 4.3 g of anexemplary compound (IR-5) (λ_(max)=795 nm, ε=270,000, in methanol).

2. Synthesis of Exemplary Compound (IR-18) Included in General Formula(2)

19 g of 1H, 1H, 2H, 2H-perfluorooctanethiol and 2.70 μg of sodiummethoxide were dissolved in 100 ml of methanol, and to thus solution wasadded, a little bit at a time, 37.8 g of2-(2-(2-chloro-3-(2-(1,3-dihydro-1,1,3-trimethyl-2H-benzo[e]-indol-2-ylidene)-ethylidene)-1-cyclohexen-1-yl)-ethenyl)-1,1,3-trimethyl-1H-benz[e]indolium, p-toluene sulfonate (a compound used as infraredabsorption agent in JP-A No. 7-271029, Example (1)) portion-wise whilestirring at room temperature. After stirring for 4 hours, the reactionsolution was poured into 1,000 ml of water. A precipitate was filtratedoff, and washed with water to obtain 27.5 g of the exemplary compound(IR-18) (λ_(max)=820 nm, ε=230,000, in methanol).

3. Synthesis of Exemplary Compound (IR-24) Included in General Formula(3)

51.8 g of 2-(N-ethylanilino)ethanol and 31.7 g of triethylamine weredissolved in 320 ml of acetone, and to this solution 24.9 g of acetylchloride was slowly added dropwise while stirring under ice cooling.This mixture was stirred for 3 hours at room temperature, and thereaction solution was poured into 500 ml of water. An organic layer wasextracted with ethyl acetate, washed with water, and then dried oversodium sulfate. The solvent was distilled off under reduced pressure toobtain 64.9 g of 2-(ethylphenylamino)ethyl acetate.

To 16.1 g of dimethylformamide was dropwise added 33.7 g of phosphorylchloride while stirring under ice cooling. Further, 30 ml of a solutionof 41.5 g of 2-(ethylphenylamino)ethyl acetate in dimethylformamide wasadded dropwise, and this mixture was stirred for 5 hours at 40° C. Thisreaction solution was poured into 1,000 ml of sodium acetate aqueoussolution. An organic layer was extracted with ethyl acetate, washed withwater, and then dried over sodium sulfate. The solvent was distilled offunder reduced pressure, and the resulting coarse product was purified bysilica gel column chromatography to obtain 35.3 g of2-(ethyl(4-formylphenyl) amino) ethyl acetate.

23.5 g of 2-(ethyl(4-formylphenyl)amino)ethyl acetate, 4.91 g ofcyclohexanone and 150 ml of ethanol were mixed and to this was added anaqueous solution (25 ml) of 2.2 g of sodium hydroxide while stirring at50° C. This mixture was further stirred for 5 hours. After cooling toroom temperature, a precipitate was filtrated, and washed with a smallamount of ethanol and water to obtain 41.5 g of2,6-bis((4-(ethyl(2-hydroxyethyl) amino)phenyl)methylene)cyclohexan-1-on e.

35.9 g of2,6-bis((4-(ethyl(2-hydroxyethyl)amino)phenyl)methylene)-cyclohexan-1-one,16.2 g of triethylamine and 160 ml of acetone were mixed and to this wasadded 69.2 g of perfluorooctanoyl chloride while stirring under icecooling. After stirring for 4 hours at room temperature, this reactionsolution was poured into 900 ml of water, and a precipitate wasfiltrated to obtain 89.3 g of2,6-bis((4-(ethyl(2-perfluorooctanoyloxyethyl)amino)phenyl)methylene)cyclohexane-1-one.

24.8 g of2,6-bis((4-(ethyl(2-perfluorooctanoyloxyethyl)amino)phenyl)methylene)cyclohexane-1-one,150 g of tetrahydrofuran and 100 g of tetrahydrofurfuryl alcohol weremixed, and to this was added 0.76 g of sodium borate hydride whilestirring. This mixture was stirred for 6 hours at 50° C. To this wasadded 20 g of acetic acid and 3.7 g of a 60% perchloric acid aqueoussolution, and a precipitate was filtrated off to obtain 16.1 g of theexemplary compound (IR-24) (λ_(max)=782 nm, ε190,000, in acetone).

4. Synthesis of Exemplary Compound (IR-29) Included in General Formula(4)

14.3 g of stearylmercaptane, 2.70 g of sodium methoxide and 500 ml ofmethanol were mixed, and to this solution was added, a little bit at atime, 37.8 g of2-(2-(2-chloro-3-(2-(1,3-dihydro-1,1,3-trimethyl-2H-benzo[e]-indol-2-ylidene)-ethylidene)-1-cyclohexen-1-yl)-ethenyl)-1,1,3-trimethyl-1H-benz[e]indolium,p-toluene sulfonate (the compound used as the infrared absorption agentin JP-A No. 7-271029, Example (1)) while stirring at room temperature.After stirring for 4 hours, this reaction solution was poured into 1,000ml of water. A precipitate was filtrated off, and washed with water toobtain 26.8 g of the exemplary compound (IR-29) (λ_(max)=814 nm,ε=260,000, in methanol).

Example 1 Example of a Positive Image-Formation Material

[Production of Substrate]

An aluminum plate (material 1050) having a thickness of 0.3 mm wasdegreased by washing with trichloroethylene. Then, the surface thereofwas grained using a nylon brush and a pumice-water suspension of 400mesh, and washed thoroughly with water. This plate was immersed in a 25%aqueous sodium hydroxide solution at 45° C. for 9 seconds to effectetching, and washed with water, then further immersed in a 20% nitricacid solution for 20 seconds, and washed with water. The etched amountof the grained surface in this procedure was about 3 g/m². Then, theplate was treated with a current density of 15 A/dm³ using 7% sulfuricacid as an electrolyte, to form thereon a direct current anodized filmof 3 g/m². Then, the plate was washed with water and dried, a primersolution described below was applied thereto, and the film was dried at90° C. for 1 minute. The amount of the film applied after drying was 10mg/m².

Primer solution β -Alanine 0.5 g Methanol  95 g Water   5 g

On the obtained substrate, the following photosensitive layer coatingsolution [A] was applied to give a coating amount of 1.8 g/m², to obtaina planographic printing plate [A-1].

(Photosensitive Layer Coating Solution [A])

m,p-Cresol novolak (m/p ratio = 6/4, weight-average molecular  1.0 gweight 3,500, containing unreacted cresol 0.5% by weight) Infraredabsorption agent (exemplary compound IR-5)  0.2 g Dye obtained bysetting counter ion in Victoria Pure Blue BOH 0.02 g to1-naphthalenesulfonate anion Fluorine-based nonionic surfactant (tradename: Megafac F-177, 0.05 g Dainippon Ink & Chemicals Inc.)γ-Butyrolactone   3 g Methyl ethyl ketone   8 g 1-Methoxy-2-propanol   7g

Examples 2 and 3

Planographic printing plates [A-2] and [A-3] were obtained in the samemanner as in Example 1 except that the infrared absorption agentcompounded in the photosensitive layer coating solution [A] in Example 1was replaced with the exemplary compounds described in the followingtable 1.

Comparative Example 1

A planographic printing plate [A-C] was obtained in the same manner asin Example 1 except that the infrared absorption agent compounded in thephotosensitive layer coating solution [A] in Example 1 was replaced withIR-792 perchlorate (manufactured by Sigma Aldrich Japan K.K.) having thefollowing structure.

Example 4

The following photosensitive layer coating solution [B] was applied to asubstrate obtained in the same manner as in Example 1 such that acoating amount was 1.6 g/m², to obtain a planographic printing plate[B-1].

(Photosensitive Layer Coating Solution [B])

m,p-Cresol novolak (m/p ratio = 6/4, weight-average molecular  0.3 gweight 3,500, containing unreacted cresol 0.5% by weight) Copolymer 1described in JP-A No. 11-348443  0.7 g Bis(4-hydroxyphenyl)sulphone  0.1g Infrared absorption agent (exemplary compound IR-5)  0.15 gp-Toluenesulfonic acid 0.002 g Dye obtained by setting counter ion inVictoria Pure Blue BOH  0.02 g to 1-naphthalenesulfonate anionFluorine-based nonionic surfactant (trade name: Megafac F-177,  0.05 gDainippon Ink & Chemicals Inc.) γ-Butyrolactone    8 g Methyl ethylketone    8 g 1-Methoxy-2-propanol    4 g

Examples 5 to 6

Planographic printing plates [B-2] and [B-3] were obtained in the samemanner as in Example 4 except that the infrared absorption agentcompounded in the photosensitive layer coating solution [B] in Example 4was replaced with the exemplary compounds described in the followingtable 1.

Comparative Example 2

A planographic printing plate [B-C] was obtained in the same manner asin Example 4 except that the infrared absorption agent compounded in thephotosensitive layer coating solution [B] in Example 4 was replaced withIR-792 perchlorate (manufactured by Sigma Aldrich Japan K.K.).

[Evaluation of Performance of Planographic Printing Plates]

Regarding the positive planographic printing plates of Examples 1 to 6and Comparative Examples 1 and 2 produced as described above, evaluationof performance was conducted according to the following standards.Evaluation results are shown in Table 1.

-Sensitivity-

The obtained planographic printing plates were exposed using asemiconductor laser having an output of 500 mW, a wavelength of 830 nmand a beam diameter of 17 μm (1/e²) at a main scanning rate of 5 m/sec.Then, development was conducted using an automatic developing machine(manufactured by Fuji Photo Film Co., Ltd.; trade name: PS Processor 900VR) charged with a developing solution DP-4 and a rinse liquid FR-3(1:7), both manufactured by Fuji Photo Film Co., Ltd. In this procedure,DP-4 was diluted with water at 1:8. Line widths of non-image partsobtained using this developing solution were measured, and anirradiation energy of the laser that corresponded to these line widthwas calculated as sensitivity. Values of measured sensitivity are shownin Table 1.

TABLE 1 Planographic Infrared absorption printing plate agentSensitivity (mJ/cm²) Example 1 A-1 IR-5 175 Example 2 A-2 IR-18 175Example 3 A-3 IR-29 185 Comparative A-C IR-792 perchlorate 210 Example 1Example 4 B-1 IR-5 160 Example 5 B-2 IR-18 165 Example 6 B-3 IR-24 155Comparative B-C IR-792 perchlorate 190 Example 2

As is apparent from Table 1, it was found that a planographic printingplate using the image-formation material of the present invention hashigher sensitivity and more excellent image-forming property as comparedwith a known infrared absorption agent.

Examples 7 to 10 Examples of Negative Image-Formation Materials

(Photosensitive Layer Coating Solution [C])

Diazonium salt of general formula (1) used in Example 1 de- 0.15 gscribed in JP-A No. 11-352679 Infrared absorption agent (exemplarycompound IR-5) 0.10 g Poly p-hydroxystyrene resin (weight-averagemolecular 1.5 g weight 10,000) Crosslinking agent (having the structurebelow) 0.50 g Fluorine-based nonionic surfactant (trade name: Megafac F-0.03 g 177, Dainippon Ink & Chemicals Inc.) Methyl ethyl ketone 15 g1-Methoxy-2-propanol 10 g Methyl alcohol 5 g

Crosslinking agent

In a photosensitive layer coating solution [C] having theabove-mentioned composition, the kind of infrared absorption agent waschanged as shown in Table 2, to obtain four kinds of coating solution[C-1] to [C-4]. These solutions were applied in the same manner as inExample 1, and dried at 100° C. for 1 minute, to obtain negativeplanographic printing plates [C-1] to [C-4] as Examples 7 to 10. Thecoating weight after drying was 1.3 g/m².

The obtained negative planographic printing plates [C-1] to [C-4] wereexposed with a semiconductor laser emitting infrared light having awavelength of 830 nm, the same as in Example 1. After exposure, theplates were heated for 1 minute in an oven at 140° C., and then passedthrough an automatic developing machine charged with the developingsolution DP-4 (1:4) and rinse liquid FR-3 (1:7), manufactured by FujiPhoto Film Co., Ltd. In each case, an excellent negative image wasobtained.

Comparative Example 3

A negative planographic printing plate [C—C] (Comparative Example 3) wasobtained in the same manner as in Examples 7 to 10, except that theinfrared absorption agents used in Examples 7 to 10 were replaced withIR-792 perchlorate in the photosensitive layer coating solution [C].

The obtained planographic printing plate [C—C] was subjected toexposure, heat treatment and development in the same manner as forExamples 7 to 10, and sensitivity was measured in the same manner as forExamples 1 to 6. The results are shown in Table 2.

TABLE 2 Planographic Infrared absorption printing plate agentSensitivity (mJ/cm²) Example 7 C-1 IR-5 125 Example 8 C-2 IR-18 115Example 9 C-3 IR-24 115 Example 10 C-4 IR-29 125 Comparative C-C IR-792160 Example 3 perchlorate

As is apparent from Table 2, it was found that, also in the case ofusing a negative image-formation material, a planographic printing plateusing the infrared absorption agent of the present invention has highersensitivity and more excellent image-forming property as compared with aknown infrared absorption agent.

Examples 11 to 12 Examples of Negative Image-Formation Material

(Photosensitive layer coating solution [D]) lodonium salt of thestructure below 0.67 g Infrared absorption agent 0.27 g Allylmethacrylate-methacrylic acid copolymer 3.3 g (molar ratio 87:13, MW =100,000) Dipentaerythritol hexaacrylate 3.3 g (DPHA) [manufactured byNippon Kayaku Co., Ltd.] Dye obtained by setting counter ion in VictoriaPure Blue 0.13 g BOH to 1-Naphthalenesulfonate anion Fluorine-basednonionic surfactant (trade name: Megafac F- 0.1 g 177, Dainippon Ink &Chemicals Inc.) Methyl ethyl ketone 33 g 1-Methoxy-2-propanol 20 gMethyl alcohol 26 g

Iodonium salt

In a photosensitive layer coating solution [D] having theabove-mentioned composition, the kind of infrared absorption agent waschanged as shown in Table 3 to obtain two kinds of coating solution,[D-1] and [D2]. These solutions were applied on to a substrate in thesame manner as for Example 1, and dried at 115° C. for 45 seconds, toobtain negative planographic printing plates [D-1] and [D-2] as Examples11 and 12. The coating weight after drying was 1.4 g/m².

The obtained negative planographic printing plates [D-1] and [D-2] wereexposed with a semiconductor laser emitting infrared light having awavelength of 830 nm, the same as in Examples 1 to 10, and then passedthrough an automatic developing machine charged with DN-3C (1:2), adeveloping solution manufactured by Fuji Photo Film Co., Ltd., and therinse liquid FR-3 (1:7). In both cases, an excellent negative image wasobtained.

Comparative Example 4

A negative planographic printing plate [D-C] (Comparative Example 4) wasobtained in the same manner as in Examples 11 to 12 except that theinfrared absorption agent in the photosensitive layer coating solution[D] used in Examples 11 to 12 was replaced with IR-786 perchlorate(manufactured by Sigma Aldrich Japan K.K.).

The obtained planographic printing plate [D-C] was subjected toexposure, heat treatment and development in the same manner as forExamples 11 to 12, and sensitivity was measured in the same manner asfor Examples 1 to 10. The results are shown in Table 3.

TABLE 3

IR-786 perchlorate Planographic Infrared Sensitivity printing plateabsorption agent (mJ/cm²) Example 11 D-1 IR-18 140 Example 12 D-2 IR-29145 Comparative D-C IR-786 160 Example 4 perchlorate

From the results shown in Table 3, it was found that both of theplanographic printing plates of Examples 11 and 12 had highersensitivity and more excellent image-forming property as compared withthat obtained by using a known infrared absorption agent.

From the above-described examples, it was found that the presentinvention can provide an image-formation material having highsensitivity and also excellent image-forming property, by use of theabove-described specific infrared absorption agent.

Further, a planographic printing plate using this image-formationmaterial can perform direct plate production with an infrared laser, andhas high sensitivity and excellent image-forming property.

The image-formation material of the present invention shows highsensitivity to an infrared laser and excellent image formation property.Further, a planographic printing plate using this image-formationmaterial provides effects such that direct plate production is possiblewith an infrared laser-, sensitivity is high and image formationproperty is excellent.

1. An infrared absorber comprising, in a molecule thereof, afluorine-containing substituent which has at least 5 fluorine atoms,wherein said infrared absorber is represented by general formula (1) asfollows:

in which formula: each of R_(F) ¹ and R_(F) ² independently represents afluorine-containing substituent having at least 5 fluorine atoms; eachof X¹ and X² independently represents —CR⁹R¹⁰—, —S—, —Se—, —NR¹¹—,—CH═CH— or —O—; R¹ to R⁸ each independently represents a hydrogen atom,alkyl group, alkoxy group or halogen atom; R¹ to R⁸ may represent aplurality of atoms such that at least one of pairs R¹ and R³, R² and R⁴,R⁵ and R⁷, R⁶ and R⁸, R¹ and X¹, and R² and X² can be mutuallyconnectable to form an aliphatic 5-membered ring or 6-membered ring, anaromatic 6-membered ring or a substituted aromatic 6-membered ring; R⁹and R¹⁰ each independently represents an alkyl group, or represent ═CH—which are combined to form a ring; R¹¹ represents an alkyl group; Z¹represents a heptamethine group, which may have one or more substituentsselected from the group consisting of alkyl groups, halogen atoms, aminogroups, arylthio groups, alkylthio groups, aryloxy groups, alkoxygroups, barbituric groups and thiobarbituric groups, and which mayinclude a cyclohexene or cyclopentene ring formed by mutually bondingsubstituents on two methine carbons of the heptamethine group, whichring may further have a substituent selected from the group consistingof alkyl groups and halogen atoms; and X⁻ represents a counter ionrequired for neutralizing an electric charge.
 2. An infrared absorbercomprising, in a molecule thereof, a fluorine-containing substituentwhich has at least 5 fluorine atoms, wherein said infrared absorber isrepresented by general formula (2) as follows:

in which formula: R_(F) ³ represents a fluorine-containing substituenthaving at least 5 fluorine atoms; X³ represents —NH—, —O— or —S—; eachof R¹² and R¹³ independently represents an alkyl group; each of X¹ andX² independently represents —CR⁹R¹⁰—, —S—, —Se—, —NR¹¹—, —CH═CH— or —O—;R¹ to R⁸ each independently represents a hydrogen atom, alkyl group,alkoxy group or halogen atom; R¹ to R⁸ may represent a plurality ofatoms such that at least one of pairs R¹ and R³, R² and R⁴, R⁵ and R⁷,R⁶ and R⁸, R¹ and X¹, and R² and X² can be mutually connectable to forman aliphatic 5-membered ring or 6-membered ring, an aromatic 6-memberedring or a substituted aromatic 6-membered ring; R⁹ and R¹⁰ eachindependently represents an alkyl group, or represent ═CH— which arecombined to form a ring; R¹¹ represents an alkyl group; X⁻ represents acounter ion required for neutralizing an electric charge; and Z²represents a polymethine chain of at least 5 carbon atoms.
 3. Aninfrared absorber comprising, in a molecule thereof, afluorine-containing substituent which has at least 5 fluorine atoms,wherein said infrared absorber is represented by general formula (3) asfollows:

in which formula: each of R_(F) ⁴, R_(F) ⁵, R_(F) ⁶ and R_(F) ⁷independently represents a fluorine-containing substituent having atleast 5 fluorine atoms or an alkyl group, and at least one of R_(F) ⁴,R_(F) ⁵, R_(F) ⁶ and R_(F) ⁷ represents a fluorine-containingsubstituent having at least 5 fluorine atoms; Z³ represents apentamethine group, which may have a substituent selected from the groupconsisting of halogen atoms, hydroxyl groups, alkyl groups optionallyhaving a further substituent, aryl groups optionally having a furthersubstituent and heterocyclic groups, and which may also contain acyclohexene or cyclopentene ring formed by mutually bonding substituentson two methine carbons of the pentamethine group, which ring may furtherhave a substituent selected from the group consisting of alkyl groupsand halogen atoms; and X⁻ represents a counter ion required forneutralizing an electric charge.
 4. An infrared absorber comprising apolymethine chain of at least 5 carbon atoms and an alkyl group of atleast 8 carbon atoms, said alkyl group being connected to thepolymethine chain via any of nitrogen, oxygen and sulfur.
 5. An infraredabsorber according to claim 4 wherein said infrared absorber isrepresented by general formula (4) as follows:

in which formula: R¹⁴ represents an alkyl group of at least 8 carbonatoms; X³ represents —NH—, —O— or —S—; each of R¹² and R¹³ independentlyrepresents an alkyl group; each of X¹ and X² independently represents—CR⁹R¹⁰—, —S—, —Se—, —NR¹¹—, —CH═CH— or —O—; R¹ to R¹ each independentlyrepresents a hydrogen atom, alkyl group, alkoxy group or halogen atom;R¹ to R⁸ may represent a plurality of atoms such that at least one ofpairs R¹ and R³, R² and R⁴, R⁵ and R⁷, R⁶ and R⁸, R¹ and X¹, and R² andX² can be mutually connectable to form an aliphatic 5-membered ring or6-membered ring, an aromatic 6-membered ring or a substituted aromatic6-membered ring; R⁹ and R¹⁰ each independently represents an alkylgroup, or represent ═CH— which are combined to form a ring; R¹¹represents an alkyl group; X⁻ represents a counter ion required forneutralizing an electric charge; and Z² represents a polymethine chainof at least 5 carbon atoms.